The Orange Book
Tetra Pak Processing Systems AB SE-221 86 Lund, Sweden. www.tetrapak.com
ISBN 91-3428-4 Further copies of The Orange Book can be obtained from your local Tetra Pak company. Editor
Ulla Ringblom Production
Pyramid Communication AB Printer: Ruter Press Printed in 2004 ©
No part of The Orange Book may be duplicated in any form without the source being indicated (Tetra Pak). To the best of our knowledge the information presented in this book is correct. Nevertheless, Tetra Pak disclaims all responsibility for any detrimental effects resulting from the way in which the information is used.
Sharing an experience A mine of information
Because of its refreshing taste and wholesome nature, orange juice dominates the fruit juice market. It is unique among juices in that the consumer can easily compare its sensory properties with those of the fresh fruit or juice squeezed directly from fresh oranges. This puts high demands on orange juice producers to deliver the same level of quality, or as near as possible, as that consumers expect from fresh fruit. The challenge is particularly tough because orange juice is a complex beverage sensitive to the way it is treated. Over the years, Tetra Pak has been closely involved with orange juice products. We believe that some of this experience could also be of interest to our customers. As a supplier of both processing equipment and packaging systems, Tetra Pak has hands-on competence with all steps in the production chain, from the fruit tree to the distribution of packaged orange juice. This is what we would like to share with you in the form of this book.
From bulk concentrate and onwards, much of what is described in The Orange Book is also valid for orange nectars and other types of fruit juices. However, the production requirements for pure orange juice are usually more stringent in order to satisfy consumer expectations for this product. This book focuses solely on orange juice, but Tetra Pak also has extensive know-how in the processing and packaging of many other types of fruit juices. A number of tools help you extract information readily from this book. A glossary explains familiar expressions used in the citrus industry, and a list of literature is given for further reading. Metric units are used throughout this book except when other specific units are commonly used. A list of conversion factors allows you to convert between different units. We hope you will find The Orange Book useful in providing consumers with the most enjoyable fruit juice provided by nature.
A journey with juice
The Orange Book follows the complete journey of orange juice. It begins with the various types of orange fruit, proceeds through all the processing and packaging steps, and ends with the distribution of the end product to consumers. Along the way there is a chance to look at market information, juice quality and categories, the trading and shipping of products, and industry standards and regulations. Consideration is given throughout to the factors that influence end-product quality, including the role of flavour and product blending.
The first edition of The Orange Book was well received in 1997, and as it went out of print it is followed by this revised edition. Valuable comments have been received on the book from many sources in the citrus industry. Tetra Pak would particularly like to thank the following persons for their review of relevant sections in the book and suggestions on how to improve it: Professor Robert Braddock of the University of Florida, Antonio Carlos Gonçalves of Louis Dreyfus Citrus, Dr. Barrie Preston of Döhler-Eurocitrus, and Martin Greeve, Chairman of the AIJN Code of Practice Expert Group.
Contents 1. THE ORANGE FRUIT AND ITS PRODUCTS
1.1 The fruit’s origin and important varieties
1.2 A global overview 1.2.1 Large-scale development 1.2.2 Orange crop diseases
3 4 4
1.3 Bridging the seasons
1.4 Fruit selection
1.5 Inside an orange
1.6 Squeezing out every drop
1.7 Primary and secondary products
1.8 Major orange-producing regions 1.8.1 Brazil 1.8.2 Florida
10 10 12
1.9 Other regions
2. ORANGE JUICE QUALITY AND CATEGORIES
2.1 Juice quality 2.1.1 Defining quality 2.1.2 Quality specifications
18 18 19
2.2 Important properties of orange juice 2.2.1 Sugars and acids 2.2.2 Cloud and pulp 2.2.3 Flavour 2.2.4 Colour 2.2.5 Promoting health
20 20 22 23 25 26
2.3 Orange juice categories 2.3.1 Ready-to-drink orange juice 2.3.2 Concentrated orange juice
28 28 29
2.4 Regulations governing juice origin
3. THE SUPPLY CHAIN AND GLOBAL CONSUMPTION OF ORANGE JUICE
3.1 The chain of supply 3.1.1 Growers 3.1.2 Types of fruit processor 3.1.3 Blending houses 3.1.4 Juice packers 3.1.5 Soft drink producers
32 33 34 35 36 37
3.2 World market pricing for bulk juice products
3.3 FCOJ commodity trading and the futures market
3.4 Import duties and juice imports 3.4.1 Import duties with some typical examples
3.5 Global orange juice consumption 3.5.1 Per capita orange juice consumption
4. PRINCIPLES OF PROCESSING ORANGE JUICE
4.1 Impact of processing on juice quality 4.1.1 Raw materials 4.1.2 Processing 4.1.3 Impact of long-term bulk storage
46 47 47 49
4.2 Air/oxygen in the product 4.2.1 Sources of air/oxygen 4.2.2 Problems caused by air/oxygen in the product 4.2.3 Principles of deaeration
4.3 Microbiology of orange juice 4.3.1 Relevant microorganisms in orange juice 4.3.2 Microflora of different types of orange juice 4.3.3 Influence of raw materials 4.3.4 Sanitation
4.4 Pasteurisation 4.4.1 Purpose of pasteurisation 4.4.2 Inactivation of enzymes 4.4.3 Inactivation of microorganisms 4.4.4 Time-temperature conditions for pasteurisation
59 59 59 61
5. FRUIT PROCESSING
5.1 Processing plant overview
5.2 Orange juice production steps
5.3 Fruit reception
5.4 Juice extraction 5.4.1 Extractor types 5.4.2 The squeezer-type extractor 5.4.3 The reamer-type extractor 5.4.4 Down stream of the juice extractors
68 68 69 71
5.6 NFC production 5.6.1 Oil reduction 5.6.2 Primary pasteurisation 5.6.3 Deaeration 5.6.4 Long-term frozen storage 5.6.5 Aseptic storage in tanks 5.6.6 Aseptic storage in bag-in-box containers 5.6.7 Reprocessing of NFC
74 75 76 76 76 77
54 57 58 58
5.7 Concentrate production 5.7.1 Tubular evaporator systems 5.7.2 Plate evaporator systems 5.7.3 Homogenisation 5.7.4 The centrifugal evaporator 5.7.5 Essence recovery 5.7.6 Concentrate storage 5.7.7 Alternative concentration methods
79 79 80 81 82 82 83 83
5.8 Peel oil (cold-pressed oil) recovery 5.8.1 Straining and concentration step 5.8.2 Polishing 5.8.3 The winterisation process 5.8.4 d-Limonene recovery systems
84 84 85 85 85
5.9 Feed mill operations
5.10 Pulp production 5.10.1 Production factors which affect commercial pulp quality 5.10.2 Process steps in pulp production
87 88 88
5.11 Pulp wash production
5.12 Essence recovery
6. TRANSPORT AND HANDLING OF BULK PRODUCTS
6.1 Packing and shipping preferences
6.2 Bulk shipping of FCOJ 6.2.1 From Brazil to Europe
6.3 Bulk shipping of NFC 6.3.1 Frozen NFC shipments 6.3.2 Bulk units for aseptic NFC shipments 6.3.3 Bulk shipping of aseptic NFC by sea 6.3.4 Transport of bulk product versus retail packaged product
7.1 An overview of juice packer operations 7.1.1 General requirements for juice packer lines 7.1.2 Process lines 7.2 Raw material reception and handling 7.2.1 Tanks for concentrate storage 7.2.2 Drums with frozen concentrate 7.2.3 Drums containing solid frozen products 7.2.4 Aseptic bag-in-box containers 7.2.5 Tanks for NFC 7.2.6 Reclaim product
97 99 99
6.4 Shipping costs
6.5 Terminals for receiving orange juice 6.5.1 Terminals for bulk FCOJ 6.5.2 Terminals for bulk aseptic NFC
100 100 101
6.6 Blending house operations
PROCESSING AT THE JUICE PACKER
103 105 105 105 110 110 111 111 112 112 112
7.3 Water treatment 7.3.1 Water quality 7.3.2 Water treatment methods 7.3.3 In-plant distribution of product water 7.3.4 Deaeration of water
113 113 114
7.4 Blending 7.4.1 Blending of nectars and fruit drinks 7.4.2 Defining the blending formula 7.4.3 Savings made by accurate blending 7.4.4 Comparison of blending methods 7.4.5 Batch blending systems 7.4.6 In-line blending systems 7.4.7 How a refractometer works 7.4.8 How a density meter works
116 116 117 118 118 119 120 121 122
7.5 Pasteurisation and deaeration 7.5.1 Selecting the heat exchanger 7.5.2 The pasteurisation process 7.5.3 Deaeration 7.5.4 System design 7.5.5 Process control 7.5.6 Control of pasteurisation units
122 123 124 125 126 126 127
7.6 Aseptic buffer 7.6.1 Operational steps
7.7 Hot filling 7.7.1 Process description
7.8 Aseptic transfer of NFC
7.9 Cleaning-in-place 7.9.1 CIP procedures 7.9.2 Pigging
131 132 133
7.10 Quality control of final product 7.10.1 Microbiological control
8. ADD-BACK COMPONENTS – VOLATILE FLAVOURS AND FLOATING PULP
8.1 Volatile flavours 8.1.1 Origin of natural volatile orange flavours 8.1.2 Major constituents of flavour fractions 8.1.3 Flavour standardisation and folding of oils 8.1.4 Methods of separating and concentrating flavours 8.1.5 Creation of flavour systems
8.2 Floating pulp 8.2.1 Useful terms 8.2.2 Floating pulp properties 8.2.3 Floating pulp concentration
142 142 144 145
8.3 Components added back to juice
9. PACKAGING AND STORAGE OF ORANGE JUICE
10.2 Orange juice at the retailer 10.2.1 Distribution units 10.2.2 Handling at the retailer
140 141 142
9.2 Barrier properties against oxygen 9.2.1 Vitamin C degradation 9.2.2 Colour changes 9.2.3 The impact of oxygen on storage-dependent flavour changes
152 152 154
9.3 Barrier properties against light
9.4 Barrier properties against aromas 9.4.1 Composition of orange juice aroma 9.4.2 Properties of different polymers 9.4.3 Properties of different packages 9.4.4 Consequences of flavour scalping
156 156 157 158 159
9.5 Aseptic versus nonaseptic packaging
10.1 Distribution of product to retailer 169 10.1.1 Delivery directly to the retail store 169 10.1.2 Delivery through wholesalers 169 10.1.3 Delivery to a retailer’s central depot 170
9.1 The role of packaging 9.1.1 Product quality parameters to be protected during storage 9.1.2 Factors affecting quality parameters during storage
9.6 Different packages and packaging systems 9.6.1 Carton-based packages 9.6.2 Bottles 9.6.3 Hot filling 9.6.4 Selecting the most appropriate package for a particular juice
10. FROM JUICE PACKER TO CONSUMER
171 171 172
10.3 The orange juice consumer 174 10.3.1 Regional preferences for juice categories 174 10.3.2 Who buys juice in the USA 176 10.3.3 When orange juice is consumed 176 10.3.4 Where orange juice is consumed 177 10.3.5 Why people buy orange juice 178 10.4 Orange nectars and orange drinks 179 10.4.1 Fruit nectars 179 10.4.2 Still fruit drinks 179 11. STANDARDS AND REGULATIONS
160 161 163 165
11.1 Standards governing juice composition and labelling 11.1.1 The USA and Canada 11.1.2 The European Union 11.1.3 Other major regions and countries 11.1.4 Fruit juice standards of Codex Alimentarius
182 183 184 186
11.2 The problem of adulteration 11.2.1 Protecting the consumer 11.2.2 Telling wrong from right
188 188 189
13. ABBREVIATIONS, WEIGHTS AND MEASURES
13.2 Unit conversions
13.3 Density tables for sugar solutions 199
14. FURTHER READING AND REFERENCES
14.1 Books on orange juice
14.3 Useful websites
The orange fruit and its products
In section 1 you will read about: • The origin and spread of the orange plant from Southeast Asia to the rest of the world. • Global orange production and the development of large-scale production. • Common orange crop diseases and their control by using resistant rootstocks. • The whys and wherefores of single-strength and concentrated juice.
• How the seasons are bridged to provide consumers with year-round supplies. • What’s inside an orange. • Nature’s gift. Every part of the orange can be used for producing commercial products. • Valuable by-products such as pulp, peel oil, essences and animal feed. • The most important orange-growing regions.
1. The orange fruit and its products A look inside Basically, an orange consists of juice vesicles surrounded by a waxy skin, the peel. The peel comprises a thin, coloured outer layer called the ﬂavedo and a thicker, ﬁbrous inner layer called the albedo. The endocarp, the edible portion of the fruit, includes a central ﬁbrous core and individual segments containing the juice sacs. In large processing plants the complete fruit is utilised. By-products are produced to help maximise proﬁts and minimise waste.
Summary The orange plant originated in Southeast Asia and spread gradually to other parts of the world. Today, orange juice products derive from four main groups of orange. About 65 million tonnes of oranges per annum are produced globally. Of this, around 40 % is processed into juice and the rest consumed as whole fruit. Single-strength or concentrated As juice is produced on a seasonal basis, it must be stored between seasons to ensure a year-round supply to consumer markets. Most juice is produced as frozen concentrated orange juice, FCOJ, because it can be stored for long periods of time and shipped at lower cost as it contains less water. “Not-from-concentrate” juice, NFC, which is at single strength, requires much larger volumes during storage and shipping. Most NFC produced is intended for nearby markets but its export is increasing.
Major players The two most important orange-processing regions are Brazil and the state of Florida in the US. Together these regions account for nearly 90 % of global orange juice production.
Tangerines 17 %
Lemons / Limes 11 %
1.1 The fruit’s origin and important varieties The orange is the world’s most popular fruit. Like all citrus plants, the orange tree originated in the tropical regions of Asia. Oranges are mentioned in an old Chinese manuscript dating back to 2200 BC. The development of the Arab trade routes, the spread of Islam and the expansion of the Roman empire led to the fruit being cultivated in other regions. From its original habitat, the orange spread to India, the east coast of Africa, and from there to the eastern Mediterranean region. By the time Columbus and his followers took plants to the Americas, orange trees were common in the western Mediterranean region and the Canary Islands.
Oranges 66 %
Fig. 1.1 World citrus fruit production by types 2001/02. Source: FAO
Oranges account for more than two thirds of the world production of all citrus fruits, of which other important species are the lemon, grapefruit and mandarin (see Figure 1.1).
1.2 A global overview
Italy Greece California
Florida Caribbean Mexico Central America
Fig. 1.2 The major orange-growing regions.
Four groups of fruit are of commercial signiﬁcance in the production of orange juice products: • The sweet orange, also known as the China orange, Citrus sinensis • The sour or bitter orange, also known as the Seville orange, Citrus aurantium • The mandarin orange and tangerine varieties, Citrus reticulata • Hybrid oranges (tangors) which result from various crosses between tangerines and sweet oranges.
ripens at a similar time, which allows efﬁcient harvesting and operation of processing plants. However, it also means that trees of the same variety in a grove are susceptible to the same diseases and physiological disorders. As required in different regions, bud wood may be grafted on to rootstocks known to be resistant to certain diseases or drought. During their ﬁrst few years of growth orange trees do not bear fruit, but when they do, the yield per tree increases gradually until the trees reach maturity at about 10 years old.
Of these, the sweet orange is by far the most important. In several markets, including Europe, only juice made from sweet orange varieties, Citrus sinensis, may be labelled as orange juice. To be cor rect from a horticultural viewpoint, the common name for the species Citrus reticulata is mandarin, some varieties of which are called tangerines. However, the word tangerine is often used as the common species name. Most citrus plants are propagated vegetatively by bud wood cuttings (scions – the top part that controls the type of fruit) grafted on to a different rootstock. This means that trees of the same cultivar are genetically identical and respond similarly to their environment, for example fruit
1.2 A global overview Oranges are cultivated in tropical and subtropical regions around the world. The trees can grow in a wide range of soil conditions, from extremely sandy soils to rather heavy clay loams, although they grow best in intermediate types of soil. Local growing conditions, such as climate, type of soil and grove practices, have a large inﬂuence on the quality of fruit produced and on the extracted juice. An orange variety, for example Valencia, may have quite different properties when grown in different parts of the world. The major orange-growing regions are shown in Figure 1.2.
1.2 A global overview
Approximately 65 million tonnes of oranges are produced per year worldwide. About 40 % of the total tonnage is processed, the rest being consumed as fresh fruit. Whenever possible, growers prefer to sell oranges to the fresh fruit market as their price is normally higher than for fruit sold for processing into juice. In some countries this can lead to a signiﬁcant variation in the amount of fruit processed from one year to another. Florida and Brazil are the world’s largest fruit producing countries. Here the majority of fruit harvested is processed because the orange varieties in these regions are grown for processing rather than for direct consumption. Due to the planting of new trees, world orange production continued to increase into the early 2000’s – mainly in Florida, Brazil and China. World orange production is also expected to increase further in other regions as a result of improved planting programmes, cultivating techniques, and support given to orange growers. Nevertheless, unwanted climatic effects like frost and storms, along with uncontrolled diseases of fruit trees, could reduce crops and juice yields signiﬁcantly. Recent years have seen notable ﬂuctuations in world orange production.
Others USA Brazil
100 80 60 40 20 0 Citrus fruit
Oranges for processing
Fig. 1.3 World citrus fruit production and processing, 2001/02. Source: FAO
In 1983 Brazil surpassed Florida as the world’s number one orange producer. However, new trees that were planted further south in Florida in areas less affected by frost are now bearing fruit. This has boosted Florida’s orange production signiﬁcantly and in years with good yields the state meets most of the US demand for juice. Figure 1.3 shows the estimated world citrus fruit production and processing for the 2001-02 season (mid-01 to mid-02). China has the fastest growth in citrus fruit production as a result of the intensive planting of new trees. So far, most oranges in China are consumed fresh, with only a small amount of fruit being processed. The Mediterranean is an important region for growing high-quality fruit. As more and more Mediterranean oranges are being eaten fresh, juice production is gradually declining in this region.
1.2.1 LARGE-SCALE DEVELOPMENT
Commercial cultivation of oranges intended for large-scale processing into fruit sections and juice began in Florida in the 1920’s. In the late 1940’s, frozen concentrated orange juice for home dilution was developed in the USA. This led to a rapid growth in orange juice consumption. As a result, the cultivation and processing capacity of oranges in Florida grew rapidly. However, severe frosts in Florida drastically reduced fruit yields and killed many trees during the 1960’s, 70’s and 80’s. To secure the supply of orange juice for the US market, trees were planted and large processing plants were built for orange concentrate in Brazil. The ﬁrst concentrate plant was built in Brazil in the early 1960’s and the large expansion in production capacity took place during the 70’s and 80’s. Orange processing in Brazil was established by US companies.
1.2.2 ORANGE CROP DISEASES
Like any other fruit, orange trees are susceptible to diseases. These may affect the leaves or fruit and even kill the trees. Because diseases have a large economical impact on the citrus industry, many orange-growing regions allocate large funds for research on citrus diseases, and develop more resistant fruit cultivars and cultivation methods to limit their effects.
1.3 Bridging the seasons
The characteristics of a disease will determine the appropriate response to control it. Control methods include the eradication of infected trees, chemical suppression of disease-transmitting insects and using resistant rootstock for grafting. New trees should come from controlled nurseries where seedlings are protected from airborne or soil contamination. The inspection of groves and follow-up of measures taken are important for successful control of a disease. Large eradication programmes may require special funding. In the 1940’s almost all orange trees in Brazil were destroyed following an outbreak of CTV (Citrus Tristeza Virus). New plantings were made using a different rootstock (Rangpur Lime) resistant to this virus. Among the serious citrus diseases found today is Citrus Canker, caused by Xanthomonas bacteria, that results in premature leaf and fruit drop. There is no treatment but the disease is limited by removing all trees within a 60 m radius of infected trees. CVC (Citrus Cholorosis Variegated), caused by a bacterial pathogen transmitted by the sharpshooter insect, leads to spotted leaves and small fruit. The fungal disease Citrus Black Spot causes lesions on the fruit skin, which make fruit unsuitable for consumption although it can still be processed. In 1999, a new disease was discovered in Brazil called Citrus Sudden Death (CSD) because it caused the rapid decline and death of trees with fruit and leaves still on them. It is caused by an insect-transmitted virus (similar to Tristeza) and in just a few years it has spread to important citrus areas of São Paulo State. Certain rootstocks are resistant to the Sudden Death virus. Now there is intensive replanting using resistant trees as well as in-arching, where resistant seedlings are planted next to an existing exposed tree and a by-pass is grafted onto it above the bud union. However, since these alternative rootstocks are less resistant to drought, they may require more irrigation or be used to plant groves in areas having a wetter climate.
Fig. 1.4 Harvesting seasons in Brazil and Florida.
1.3 Bridging the seasons Oranges can only ripen on the tree and the quality of the fruit begins to deteriorate immediately after picking. Therefore, the time between picking fruit and processing it into juice and other products should ideally be as short as possible – less than 24 hours – although longer periods are not uncommon. Because the orange is a seasonal fruit, each region strives to grow orange varieties with different ripening periods (see Figure 1.4). This prolongs the total harvesting period in a region and allows greater utilisation of processing equipment. To provide a year-round supply to consumers, juice must be stored to bridge the gap between seasons. Most of the juice is stored frozen as concentrate. This is called Frozen Concentrated Orange Juice, or just FCOJ as it is referred to within the industry. For the same amount of ready-to-drink (RTD) juice, concentrate requires 5–6 times less volume for storage and shipping than singlestrength juice. Thus shipping costs over long distances are signiﬁcantly higher for single-strength products like not-from-concentrate juice (NFC).
1.4 Fruit selection
Juices from early and late fruit varieties differ in quality as regards colour, sugar content, etc. To deliver products of speciﬁed and consistent quality throughout the year, concentrate suppliers blend concentrates produced from different orange varieties. Most NFC products also consist of a blend of juices extracted at different times of the season. Blending of NFC may take place within the producing country or in the importing market. The difference in quality and yield between different orange varieties is reﬂected in the range of market prices.
In plants where NFC is produced, concentrate should also be produced to make use of the “nonoptimal” fruit. In most regions, fruit best suited to NFC production is available for only part of the season. The proportion of NFC and concentrate produced in a certain region will depend on the availability of suitable fruit. At present, NFC production makes up a low percentage (25). This juice therefore requires blending.
California is the second largest orange-producing area in the US as regards quantity of fruit, but is the leading supplier of oranges to the fresh fruit market. The dry climate results in oranges with thick skin and good appearance that appeal to consumers. The state produced about 2 million tonnes of oranges during the 2001/02 season. The dominant sweet orange variety in California is Navel, a seedless variety, followed by Valencia. Both are grown primarily for the fresh fruit market. About 20 % of the crop, which for some reason is considered unattractive to consumers, is used for fruit processing. Navel orange juice has the peculiarity of developing a bitter taste after processing. In small amounts, Navel juice can be used for blending with other juices or, alternatively, the bitterness can be removed in a debittering process. Other orange-growing states in the USA are Arizona and Texas. Mexico
During the 2000/01 season, 3.8 million tonnes of oranges were produced in Mexico. Oranges make up two thirds of citrus production, limes come second with nearly 30 % of total production and their plantation area is increasing. The sweet orange crop is dominated by the Valencia variety, and most of the fruit (about 85 %) goes to the fresh fruit market. The majority of groves are small, a result of Mexican land reform and regulation that limit the size of farms. In the orange-growing areas there is often a shortage of investment money and difﬁculty in achieving effective grove management. This leads to variations in crop size and fruit quality from year to year. The production quantity of FCOJ depends on world market prices for FCOJ and raw material costs. In years with short orange supply, prices are high in the domestic fresh fruit market and so less fruit goes to processing.
Citrus production in Argentina was about 2.3 million tonnes in 2003. Oranges made up about 30 % of the total crop, the main outlet being the fresh fruit market. However, lemon is the most important citrus crop, with Argentina being the world’s largest producer of lemons, yielding about 1 million tonnes annually. Most lemons are grown in the northeast province of Tucuman. One third is exported as fresh fruit, whereas about two thirds are processed into lemon juice. Local consumption of lemons is small, and the main markets for lemon export lie in the Northern Hemisphere. Fresh fruit export to some regions has been constrained by the required protocols and phytosanitary standards, but these demands are now being increasingly met.
1.9 Other regions
China has the highest growth in citrus fruit production, with the provinces Sichuan, Guangdong and Zheijang accounting for the largest yields. In 2001, the seasonal production was about 12 million tonnes, up 50 % in 5 years, and extensive citrus tree planting is expected to further increase harvests. Nevertheless, compared with other large citrus-producing regions, fruit yields are relatively low because of poor cultivar availability and grove practices. Mandarins account for more than half of citrus harvests in China, although the trend is to reduce mandarin planting in favour of sweet orange cultivars. These include Hamlin, Valencia and Chinese varieties, which make up about 30 % of the total citrus production. Most oranges are consumed fresh with very little being processed into juice; the predominant processed product is canned mandarin. At present, the majority of oranges are harvested during a short period. Since fruit quality deteriorates rapidly after harvesting, there is only a short fresh fruit consumption period of 3–4 months. In comparison, Brazil and Florida have typical harvesting cycles with balanced yields over 7 months. Therefore there is a strong desire in China to change to fruit varieties that result in longer consumption and processing periods. The per capita growth in income has led to the rapidly increased demand for orange juice, especially in large cities. But until greater orange production can support efﬁcient processing, this demand will continue to be satisﬁed by juice imports over the next few years. Likewise, it will be difﬁcult to meet the demand for fresh fruit by domestic production in the foreseeable future, especially as the per capita fresh citrus consumption is expected to increase by 50 % over the next 10 years. Fresh fruit will continue to be the main market for domestic oranges. When China joined the WTO in 2001 it agreed to reduce tariff rates, a measure that promotes higher imports of fresh fruit and orange juice.
Citrus fruit grown in Japan consists primarily of mandarin varieties, some of which are processed into juice. However, since the strict restrictions governing fruit juice imports into Japan were lifted at the end of the 1980’s, production of mandarin juice has decreased to a low level. Imported orange juice concentrate now meets the needs of the rapidly expanding domestic juice market. Japan is also a large importer of fresh grapefruit and orange fruit, mainly from the US. Periods of economic downturn also show in declining imports. Australia
Sweet orange varieties in Australia are Navel and Valencia. Because of the high popularity of Navel – it is easy to peel and enjoyable to eat – and new plantings replacing old Valencia trees, it now accounts for about half of the crop and supplies the fresh fruit market. The orange production in Australia was about 0.6 million tonnes for the 2001/02 season, a high-yield year in the biennial yield cycle. Fruit for processing, mainly Valencia, typically accounts for 40 % of the total harvest. The Australian market for NFC has increased rapidly over the last few years and domestic producers are shifting from FCOJ to NFC production, which offers higher proﬁtability. It is difﬁcult for Australian producers to compete at world market prices for concentrate in the domestic market. Frozen concentrate now accounts for half of the juice market, mainly imported from Brazil. There is also a drive to increase the export of fresh fruit, primarily Navel, to Far East markets and increasingly to the US. As Australia has an alternate season to the US, it can supply the US market with high-quality fruit during the California Navel off-season.
1.9 Other regions
Oranges in the Mediterranean region are primarily grown for the fresh fruit market, both domestic and for export to European countries. About 15 % of regional crops goes into processing. The Mediterranean is also important for other citrus fruits. Mandarin production is about 4.5 million tonnes, or 30 % of world production. Lemons, about 3 million tonnes, account for 30 % of world supply. Spain is the largest Mediterranean producer of oranges and mandarins, the most important sweet orange varieties being Navel and Valencia. Exports to fresh fruit markets dominate. Production of orange concentrate has been reduced drastically in Spain because production costs are not competitive with world-market concentrate prices. This is despite the fact that processors in European Union countries are entitled to a signiﬁcant subsidy for purchasing fruit for juice production. NFC is produced for the European market from high-quality Valencia fruit but volumes are limited by fruit availability.
China Spain Mexico India Italy Iran Argentina Egypt Pakistan Turkey Japan South Africa
Spain is the largest “Mediterranean producer of
oranges and mandarins
Cuba Production Processing
The cultivation of seedless clementines in Spain has met with success and is much appreciated by consumers. Most fruit is exported and accounts for 50 % of world mandarin exports. In Italy, orange concentrate production has also dropped drastically because of strong international competition as regards price. However, several types of blood orange unique to Sicily are grown on the island. Juice from these oranges has created a niche market for export of both NFC and concentrate. In other cultivation areas, replacement of blonde oranges with more proﬁtable pink grapefruit is taking place.
Fig. 1.11 World citrus fruit production and processing except Brazil and Florida, 2001/02. Source: FAO
In order of crop size, the most important orangegrowing countries in the Mediterranean are Spain, Italy, Egypt, Turkey, Greece, Morocco, Syria, Algeria and Israel. About 11 million tonnes of oranges are grown in this region (2001). This represents about 20 % of world orange production, and slightly more than the current yield in Florida.
1.9 Other regions
Citrus production in Israel has been declining for many years. Orange production was less than 0.2 million tonnes in 2002, similar to grapefruit production. The drop in concentrate production has caused the closure of processing plants. Uprooting of orchards is carried out because of low proﬁtability, urbanisation and an increasing water shortage. The main varieties of sweet oranges grown in Israel are Shamouti (early) and Valencia. (Jaffa is not a fruit variety but a trade name used for fruit and juice exported from Haifa harbour.) The CMBI (Citrus Marketing Board of Israel), which encouraged the production and marketing of citrus for more than 65 years and actively built up the European juice market, closed in 2003.
South Africa has an expanding citrus industry, the main orange varieties being Valencia and Navel. Most of the orange production, some 1.3 million tonnes, is exported as fresh fruit. About 20 % goes to the domestic fresh fruit market and the same amount is processed into concentrate. Traditionally, the main export market for orange fruit was Europe, but deregulation in 1997 opened up new opportunities that led to Japan and the Middle East becoming important markets. South Africa has good potential for exporting fresh fruit to the northern hemisphere because of its alternate season. However, increased trade depends on South Africa meeting the phytosanitary requirements and production protocols of the importing regions. Changes in the organisation of the South Africa citrus industry have taken place aimed at enabling producers to meet importers’ demands more efﬁciently.
Orange juice quality and categories
In section 2 you will read about: • How quality is assessed in objective and subjective ways. • Substances and factors that are important to juice quality, such as sugars and acids, cloud, pulp, ﬂavour and colour components, and vitamin C.
• How the different quality parameters are measured. • Orange juice categories and the terms used to describe the various types of orange juice. • An introduction to regulations governing juice quality.
2. Orange juice quality and categories Juice categories and relevant terms Many special terms are used for the two main categories of orange juice products, ready-to-drink orange juice and juice concentrate. Some of these terms are referred to in the regulations of certain countries, other terms are merely used in juice marketing and trading. Standards and regulations governing product origin, juice processing, juice quality and product labelling are implemented by a number of regulatory bodies in different trading blocs. There is a general desire worldwide to harmonise the standards in force.
Summary The most important compounds that inﬂuence the quality of orange juice are sugars and acids, ﬂavour and colour components, and vitamin C. These compounds, plus cloud, are analysed to deﬁne and grade juice. The °Brix scale is used to measure sugar concentration, and juice acidity is measured by titration. There are several methods for measuring cloud and colour. Flavour is evaluated using subjective methods and is thus difﬁcult to deﬁne and measure. The deterioration of juice quality is mainly related to ﬂavour degradation, nonenzymatic browning and nutrient loss. Enzyme activity affects the mouthfeel of juice, and the formation of limonin makes juice taste bitter.
2.1 Juice quality 2.1.1 DEFINING QUALITY
For food products, quality is subjective and what is good quality must ultimately be determined by the consumer. This is also true for orange juice. The quality of orange juice as perceived by the consumer is made up of: • taste • mouthfeel • colour
TABLE 2.1 IMPORTANT QUALITY PARAMETERS FOR ORANGE JUICE Sugar content (°Brix) Acid content Ratio of °Brix to acid Cloud Pulp
However, because orange juice is traded and consumed worldwide, its quality cannot be determined solely by subjective assessments. To make assessments more objective, several quality parameters have been deﬁned. Some of these parameters are used to classify (grade) orange juice, while others are used to specify the product for trading. Table 2.1 lists the important quality parameters for orange juice.
Flavour Oil content Colour Vitamin C Defects
All the parameters listed in Table 2.1, except ﬂavour, can be determined by standard methods of analysis to give meaningful and reliable results. Orange juice ﬂavour can only be evaluated by sensory means, usually by groups of panellists. These analysis methods have been collected and published in books by, for example, Redd et al. and Kimball.
2.1 Juice quality
All processing and storage of juice on its way to the consumer should aim at maintaining the initial quality as much as possible. Equally important is the quality of water used to reconstitute orange juice, as juice made from concentrate comprises 85 % added water. The effects of processing on quality are mainly related to ﬂavour degradation, while nonoptimal storage conditions can result in juice browning, loss of vitamin C and ﬂavour changes.
TABLE 2.2 AIJN QUALITY REQUIREMENTS FOR ORANGE JUICE Properties Relative density 20/20 Corresponding °Brix
Direct juice min. 1.040 min.10
Properties L-ascorbic acid (vit. C) at end of shelf life, mg/l Volatile oils, ml/l Hydroxymethylfurfural (HMF), mg/l Volatile acid as acetic acid, g/l* Ethanol, g/l D/L Lactic acid, g/l Arsenic and heavy metals, mg/l
Reconstituted juice min. 1.045 min. 11.2
Direct juice / Reconstituted juice min. 200 max. 0.3 max. 10
2.1.2 QUALITY SPECIFICATIONS
Guidelines for quality standards for fruit juices for the European Union are speciﬁed in the Code of Practice for the evaluation of fruit and vegetable juices, published by the AIJN (see Section 11). The absolute quality requirements deﬁned in the reference guideline for orange juice are given in Table 2.2. In the USA, the US Department of Agriculture, USDA, is responsible for specifying quality standards for orange juice. To be labelled USDA Grade A, orange juice produced in Flor ida must meet the quality requirements shown in Table 2.3. The quality factors are measured on a 100point scale. If the total score is above the limit but just one of the quality factors does not meet the Grade A requirements, the juice still may not be labelled Grade A. The most important properties of orange juice that are directly related to these quality parameters are discussed in the following subsections.
max. 0.4 max. 3.0 max. 0.2 max 0.01–5.0 (various values)
* Indication of hygiene, not juice acidity. Source: AIJN Code of Practice, Reference guideline for orange juice, 2003
The basic quality of orange juice is determined at the fruit processor, i.e. by the quality of fruit accepted at the reception area, fruit storage times and the way juice is extracted. Subsequent processing steps cannot improve the main quality parameters of a given production batch. This can only be achieved by blending a particular juice with superior quality orange juice or concentrate. This is commonly done.
TABLE 2.3 REQUIREMENTS FOR USDA GRADE A ORANGE JUICE Orange juice Analytical factors °Brix Ratio (Brix:acid) Recoverable oil % v/v.
min. 11.0 12.5 – 20.5 max. 0.035
min. 11.8 12.5 – 20.5 max. 0.035
Quality factors Appearance Reconstitution Colour Flavour Defects Total score
fresh orange juice —— very good, min. 36 points very good, min. 36 points practically free, min. 18 points min. 90 points
fresh orange juice reconstitutes properly very good, min. 36 points very good, min. 36 points practically free, min. 18 points min. 90 points
2.2 Important properties of orange juice
2.2 Important properties of orange juice
HOW BRIX IS MEASURED Brix can be measured by either density measurements or by measuring the refractive index of orange juice. Both are then related to a 100 % sucrose solution. The °Brix scale is based on standard measurements at 20 °C. If the juice/ concentrate is analysed at any other temperature, a correction factor is used to equate the °Brix measurement to one made at 20 °C. To obtain the corrected °Brix value, the acid content must be determined by titration in order to read the right correction value from a table.
2.2.1 SUGARS AND ACIDS
The most important properties of orange juice are its sugar content and ratio of sugar to acid content. This ratio indicates the balance between sweetness and acidity in the juice. When the fruit matures, this ratio increases as sugars are formed and the acid content decreases. The sugars are mainly sucrose, glucose and fructose in a ratio approximating to 2:1:1. The sugar content of juice is normally expressed as °Brix. In extracted juice, the concentration of sugar typically varies from 9 °Brix for early season varieties to 12 °Brix for fruit harvested late in the season (e.g. Florida). The °Brix (degree Brix) scale, which was developed by the sugar industry, relates the sucrose concentration of a pure sucrose solution to its density at 20 °C. °Brix for orange juice not only includes the concentration of dissolved sugars but all soluble solids. Dissolved substances other than sugars will inﬂuence the result of °Brix measurements. Thus, the level of acid, the second most abundant dissolved material, is often measured and a correction of the Brix value is made. For single-strength orange juice, acid correction is small and the term °Brix is commonly used without correction to mean only the sugar content. However, in measuring °Brix of orange juice concentrate, the acid correction is important due to the much higher acid content of concentrate. Here, the term “°Brix, cor rected” is used.
Density measurements: The buoyancy of a hydrometer in a liquid is directly proportional to the density of the solution. Therefore a scale on the neck of the hydrometer can be calibrated to a °Brix scale. The °Brix is read on the scale at the point where the liquid meniscus intersects the hydrometer neck. Before measuring it is important to deaerate the juice since air in the sample can affect the result. Hydrometers are mostly used for singlestrength juice. Although a hydrometer is an inexpensive instrument, it is not very fast and requires up to 200 ml of sample. For in-line Brix measurements, one common method of measuring density is to feed the sample through an oscillating tube. When the liquid enters the tube, the frequency of the oscillations decrease. From this deviation the density can be calculated. Read more about inline density measurements in subsection 7.4.8. Measurement of light refraction: Light travels at different speeds in different media such as air, water or sugar solutions. When light passes from one medium to another it is refracted, that is, it changes direction slightly. This property of a medium can be quantiﬁed as its refractive index. The refractive index of a solution depends on its total soluble solids. Therefore °Brix can be determined by measuring the refraction of light. Either analogue or digital refractometers can be used to measure °Brix. Although refractometers are more expensive than hydrometers, they are more frequently used because they can measure over a large scale, 1–70 °Brix, and they constitute a fast method which requires very little sample, 2–3 ml. Modern refractometers can compensate for temperature, but independent correction for acids is necessary, especially for concentrates. Read more about in-line refractometer measurements in subsection 7.4.7.
°Brix = % soluble solids (w/w) °Brix, corrected = % sugar (w/w) In the laboratory, the °Brix of orange juice is analysed by measuring the juice density with a hydrometer or by measuring the refractive index of juice using a laboratory or hand refractometer. Two basic instruments used for Brix analysis are shown in Figure 2.1. Read more about in-line measurements in subsection 7.4.
Source: Dan A. Kimball, Citrus processing: Quality control and technology, 1991.
2.2 Important properties of orange juice
Density: – hydrometer
Light refraction: – hand refractometer
HOW ACIDITY (TOTAL ACIDS) IS MEASURED Juice acidity is measured using a chemical titration method. Orange juice contains acids which release hydrogen ions (H+) in solution. When a base which releases hydroxyl ions (OH ) is added to an acid media, a chemical reaction takes place which gradually turns the solution neutral.
Fig. 2.1 Examples of instruments used for °Brix measurements.
After sugars, acids are the most abundant class of soluble solids in orange juice. The acids comprise mainly citric acid and to a lesser degree malic acid. Some of the acids are in the form of salts, which give orange juice a buffering capacity. Thus even though the acid content may vary a lot, the pH of juice extracted from mature oranges is generally between 3.2 and 3.8. Total acid content (acidity) is measured by titration and is often expressed as grams citric acid per litre juice.
H+ + OH- ➞ H2O To analyse the acid content in a juice sample, a base (e.g. sodium hydroxide, NaOH) of known concentration is slowly added under agitation until a speciﬁc pH value is reached. Most ofﬁcial methods state that the end pH value should be 8.1 (AOAC*) – 8.2 (USDA). However, some producers titrate to pH 7.0 (neutral) and it is therefore important to mention the end pH together with the acid content. The change in pH can be detected by a pH electrode or by using a sensitive pH colour indicator that changes colour abruptly at pH 8.2. When the size of the juice sample, the concentration of the base and the amount of base added are known, the total concentration of acids in the juice can be calculated. In Europe, the acidity of orange juice is expressed as grams citric acid per litre juice, whereas in the USA it is expressed as grams citric acid per 100 grams juice, or % w/w.
The Brix:acid ratio is very important for taste as it is a measure of the balance between the sweet and sour sensation. As oranges ripen, the acidity decreases while the sugars increase. Therefore the Brix:acid ratio will also increase. The ratio decides the maturity of the fruit before harvesting. Maturity standards for oranges in Florida require a minimum °Brix of 9.0 and a minimum Brix:acid ratio of 10. Consumers prefer a ratio around 15 and therefore it is often necessary to increase the ratio. In the USA, the only permitted way of doing this is by blending low-ratio juice with juice of higher ratio extracted at other times of the season. In the EU, sugar may be added up to 15 g/l orange juice for balancing acidity without having to label it “sweetened”. Many other countries also allow for small amounts of sugar addition but the permitted level may vary. Therefore local legislation should be consulted for details of this. Adding sugar to juice for sweetening purposes (in higher concentrations than above) is not permitted without highly visible information on the package indicating this. Removal of acid from the juice, deacidiﬁcation, would also increase the ratio but is not permitted for orange juice in most countries. Orange juice concentrate can be bought with different ratios; typical values lie between 14 and 17.
EXAMPLE Procedure Pipette 10 ml of single-strength juice or weigh 5–10 g concentrate into a beaker. Pour sodium hydroxide (NaOH) of concentration 0.1562 N into a burette. The pH can be indicated by adding 5 drops of phenolphthalein or by using a pH meter. Titrate until a slight darkening in the juice persist or until pH 8,20. Read off the amount NaOH used from the burette. Calculation Single-strength juice: % acid = ml titration solution/10.4 Concentrate: % acid = ml titration solution/g concentrate * AOAC The association of ofﬁcial analytical chemists.
°Brix % (w/w) citric acid
2.2 Important properties of orange juice
2.2.2 CLOUD AND PULP
Cloud in orange juice is considered a desirable characteristic; it gives an opaque appearance to the juice and is important for the mouthfeel. Orange juice cloud is formed by soluble and insoluble (suspended) compounds released during juice extraction. Pectin is an important soluble cloud constituent because it increases the viscosity of the juice liquid, thereby allowing solid particles to remain suspended. So-called “cloud loss” is caused by a loss in viscosity due to reactions between pectin molecules and calcium. In the reaction, long pectin molecule chains are formed which settle to the bottom. Cloud loss leads to total separation of suspended particles, leaving an upper clear phase and a lower cloudy phase consisting of solid matter settling towards the bottom. If the same reaction between pectin and calcium takes place in orange juice concentrate, it will instead lead to gelation of the concentrate. You can read more about this in subsection 4.4. Another important contributor to the opaque appearance of juice is the suspended solids also known as pulp. The very small pulp particles called “sinking pulp” are closely related to cloud. Some sedimentation of these particles will occur during storage. This sedimentation is not related to cloud loss. Pulp is made up mainly of ruptured fruit cell walls, segment walls and core ﬁbre. Two kinds of pulp are found in juice:
HOW CLOUD AND PULP ARE MEASURED Sinking pulp Different procedures for measuring the pulp and concentration of suspended solids of orange juice are used by the industry, therefore it is often impossible to compare values from different sources. The juice sample is centrifuged in graduated tubes for a known time and speed. Solid material above a certain particle size will settle in the tubes according to the time and centrifugal force of the lab centrifuge. The recommended procedure in the juice industry is to spin the juice sample at 370 g for 10 minutes at 26 °C (USDA method), whereas the Tetra Pak method uses 3000 g for 3 minutes. The higher g-force used in the Tetra Pak method gives a more compact pulp sediment and therefore a signiﬁcantly lower reading than the recommended method for juice of the same pulp content. The sedimented quantity is expressed as volume %. Not only may the time-speed combination vary greatly from method to method, but the results may be referred to suspended solids, suspended pulp, centrifugable pulp or sinking pulp. Floating pulp Floating pulp is often measured by a sieving method. Sieves with different hole sizes are used to determine the amount and size of pulp in juice. (See subsection 8.2) Cloud stability Cloud stability is detected by measuring the transmittance of orange juice in a spectrophotometer. This analysis method is based on the fact that both soluble and insoluble solids absorb light, with the result that only a certain amount of total light entering a sample will pass through it. The orange juice sample is centrifuged to take away larger suspended particles (sinking pulp). The light transmittance of the sample serum is measured at 650 nm wavelength. The denser the cloud in orange juice, the lower the transmittance, %T. Orange juice cloud is not considered stable if the %T at 650 nm is greater than 36.
Sinking pulp, comprising particulate ﬁbres that gradually settle out with time. This type of pulp is found in all orange juices and is an important part of orange juice cloud. Typical values in single-strength juice range from 5 % to 12 %, although the results depend very much on the analysis method used.
2.2 Important properties of orange juice
Floating pulp, or cells, consisting of larger solid matter. Most of this rises to the surface of juice after it has been stirred. Floating pulp is added to concentrate or reconstituted juice. Its typical concentration in single-strength juice, if added, is 5–30 g/l (sieving method).
The ﬁrst two components have already been discussed. The following text deals with the volatile components of orange juice. ‘Volatile’ means that the compounds will vaporise from the juice at elevated temperatures. The lower the temperature at which the ﬂavour component evaporates, the more volatile is the component. As the orange ripens the volatile components are created and increase. The volatiles are of two types – water-insoluble oils and watersoluble aromas. In everyday speech, volatile components are referred to as ﬂavours. During the production of orange juice concentrate, most of the volatile ﬂavours are removed in the evaporation step by being boiled off together with water. This results in juice concentrate having a ﬂat cooked taste. However, the volatiles boiled off from juice are collected in an essence-recovery system. The orange ﬂavour in the juice can later be restored by adding back the recovered fractions. Processing and storage of juice along the whole supply chain from tree to consumer are responsible for the changes in orange ﬂavour caused by the juice losing or gaining components. Gained compounds are called off-ﬂavours (not always volatile). They are of two kinds; • natural constituents of the fruit itself (from peel and rag) • compounds formed during processing and/or storage
More information on pulp and pulp production can be found in Sections 5 and 8.
Essence oil Peel oil
Figure 2.2 The product streams that contain volatile ﬂavours in a juice processing plant.
Flavour is the complex experience of the smell, taste and mouthfeel of a product. The ﬂavour of orange juice is built up from a number of components, the most important of which are: • acids and sugars for taste • cloud for mouthfeel • volatile components for smell and taste
It is important to extract the juice so that unwanted compounds from peel and rag do not enter the juice. This is mainly achieved by avoiding too high a pressure in the juice extractors and juice ﬁnishers (see Section 5). Heat and oxygen are involved in the formation of off-ﬂavour compounds during processing and storage. However, it is still not totally clear how the compounds that affect juice ﬂavour are formed.
2.2 Important properties of orange juice
There is no reliable instrumental method of determining orange juice ﬂavour objectively, so it is carried out by sensory evaluation. As this is based on subjective judgement, the setup of sensory analyses for ﬂavour and the evaluation of results are complicated. Nevertheless, ﬂavour analyses must be carried out because of the importance of ﬂavour as a quality parameter.
The volatile ﬂavour components are found in three product fractions – peel oil, essence oil and essence aroma. To obtain good orange juice ﬂavour, components from all three fractions must be present. However, the exact blend needed for an optimal orange juice ﬂavour is still unknown. Peel oil. The recommended level of peel oil in reconstituted FCOJ is about 0.02 % v/v. When added to juice, peel oil gives body and freshness, although when used alone it can give an artiﬁcial taste. Oil levels much above 0.02 % v/v give rise to juice harshness and a burning taste.
The oil content is often equated to d-limonene concentration since d-limonene is the dominant compound present in both peel oil and essence oil. d-Limonene acts as a carrier of ﬂavours but contributes little to the ﬂavour itself. However, excess of d-limonene can give a burning taste to juice. Juice processed under USDA directives may have a maximum oil content of 0.035 % v/v. However, consumer preferences range between 0.015 and 0.020 % v/v. High levels of oil in juice result from squeezing the fruit too hard when extracting the juice (for increased yield).
Essence oil. A typical concentration of singlestrength essence oil added to orange juice from concentrate is about 0.01 % v/v. When added to juice, essence oil gives top-notes and makes the juice fruity, green and sweet. Essence aroma. The essence aroma gives topnotes to the juice and makes it fresh and sweet. A typical concentration of single-strength aroma added to orange juice is about 0.2 % v/v. Addition of this fraction is more commonly found with premium quality juice products than with standard products.
HOW OIL CONTENT IS MEASURED The analysis of volatile ﬂavours is often complicated and involves expensive instruments like a gas chromatograph. The d-limonene level can, however, be measured by a simpler titration method, the Scott method. Since it is not possible to titrate the juice directly, the oil must ﬁrst be removed from the juice. This is done by heating up a mixture of juice and alcohol; the alcohol and oil evaporate readily from the mixture since they are the most volatile components. The alcohol and oil vapours are cooled down and collected. The d-limonene content in this mixture can then be determined by titration. The titration in the Scott method is based on a chemical reaction between d-limonene and bromide. A red colour indicator is ﬁrst added to the sample and then a bromide solution is added slowly. Bromide reacts with d-limonene, and as long as there is d-limonene present in the sample the solution remains red. When the sample no longer contains any d-limonene the bromide reacts with the colour indicator instead and the red colour disappears. As the concentration of the bromide solution and the amount added to reach the colour change are known, it is possible to calculate the d-limonene content. The oil level is expressed as % v/v in 11.8 °Brix juice.
balance of ﬂavour “Acompounds from peel oil, essence oil and aroma is essential for optimal orange ﬂavour
The add-back of ﬂavours to concentrate or reconstituted juice is carried out to different degrees. Most processors add essence oil, essence aroma and additional peel oil to develop a special taste. And today, dedicated ﬂavour companies usually offer specially developed ﬂavour packages to enhance a certain desirable ﬂavour proﬁle. Further details on volatile ﬂavour fractions can be found in Section 8.
2.2 Important properties of orange juice
In juice used for concentrate production, high oil levels are not regarded as a serious problem since most of the oil is boiled off in the evaporator. However, high oil levels in juice from the extractors may indicate that other unwanted compounds have entered the juice. These nonvolatile ﬂavour compounds do not leave the juice during concentration. For NFC production, low-pressure extraction and/or downstream deoiling of extracted juice is often used to reduce the oil content to near 0.020 % v/v.
The intense colour of orange juice is mainly due to compounds called carotenoids. Colour, which should be bright yellow to orange-red and not too pale, is an important quality parameter. The fact that the USDA regards colour scores and ﬂavour scores as equally important for orange juice shows the signiﬁcance of colour.
HOW COLOUR IS MEASURED Colour is an important quality parameter but it is difﬁcult to deﬁne and measure. The main methods used to evaluate colour are presented below.
Orange juice should have no noticeable trace of bitterness. Although even very small amounts of bitter substances are detectable by the consumer, bitterness is not a common problem for orange varieties normally used for processing. Some orange varieties mainly intended for the fresh fruit market such as Navel and Shamouti contain a precursor (a chemical substance that gives rise to another more important substance) of a very bitter compound called limonin. The precursor itself is not bitter, which explains why fresh fruit and freshly extracted juice of these varieties do not taste bitter. But when the juice sacs are ruptured during extraction, the limonin precursor enters juice where it is rapidly converted to limonin. A debittering process involving ultraﬁltration and adsorbing separated bitter components on to resin can be used to remove the bitter taste. For more information see Braddock, 1999.
Known colour standards An example of this subjective method is the set of USDA colour tubes. One merely matches the colour of the orange juice sample with one of six colour standards in glass tubes. The comparison should be done under a deﬁned light intensity around 150 candela. Colorimetry A colorimeter emits a ﬂash of light from a pulsed xenon arc lamp to illuminate a juice sample and then measures the reﬂected light. The measured colour is then expressed according to the L, a and b scale. The L axis indicates lightness of colour, the a axis indicates the colour range from red to green, and the b axis indicates the colour range from yellow to blue. Although colorimetric measurements are not subjective, meaningful interpretation of results can only be made after fairly long experience. The colorimeter can also be calibrated to known standard colour tubes to make the colour measurements easier. Spectrophotometry The colour change that may occur in orange juice during storage is often called browning and is measured with a spectrophotometer. All cloud material is removed from the juice sample and the light absorbed by clear juice is measured at 420 nm wavelength. A wavelength of 420 nm is selected because the more red-brown the sample is, the more light will be absorbed at this wavelength. The higher the absorption, the more accurate the results.
2.2 Important properties of orange juice
In dry and cooler climates such as in the Mediterranean, the colour of juice is well developed, while in hotter and more humid climates like that of Florida the pigments are diluted and thus juice has less colour. The only legal way to enhance colour is to blend the juice in question with another orange juice with a higher colour score (e.g. from Valencia oranges). In the USA it is also allowed to add up to 10 % tangerine juice to early season orange juice. Tangerine juice contains more carotenoids and therefore has stronger colour than most other citrus varieties. Colour can be measured by comparing the juice with known colour standards in glass tubes, or by using a colorimeter. Off-colours result primarily from formation of brown compounds that dull the natural colour of juice, not by changes in the pigments themselves. The colour pigments of orange juice are quite heat-stable compared with colour pigments in other foods. The formation of brown-coloured compounds occurs after excessive heat treatment or long storage at room temperature.
TABLE 2.4 AVERAGE VITAMIN C CONTENT IN SOME FRUITS Fruit
Peach Apple Blackberry Kumquat Grapefruit Orange Papaya Kiwi fruit Strawberry Guava Blackcurrant
Average vitamin C, mg per 1000 g edible fruit 80 80 210 380 390 530 620 630 660 1840 2100
Source: Svenska statens livsmedelsverk, Livsmedelstabell
Typical values for vitamin C in freshly extracted juice range from 450 to 600 mg/litre. Provided that the production procedures are correct, only a small loss of vitamin C occurs during the initial processing into concentrate. More signiﬁcant losses may occur during processing at the juice packer and during ambient storage. Typical values for orange juice when consumed range from 200 to 400 mg/litre. Vitamin C is essential for the synthesis of collagen, the most abundant protein in mammals. Collagen is the major ﬁbrous element of skin, bone, blood vessels and teeth. A lack of vitamin C leads to scurvy, which causes loss of teeth, bleeding skin and ulcers. Vitamin C is sometimes suggested to have an anticancer effect by its reaction with and inactivation of free radicals in the body. A wide range of other beneﬁcial effects of vitamin C are also suggested. However, contrary to popular belief, it has never been shown clinically that vitamin C has a preventive effect on the common cold.
2.2.5 PROMOTING HEALTH
A number of compounds present in juice contribute to its health-promoting image. Some of these are discussed below. Ascorbic acid
Ascorbic acid – vitamin C – is the most important nutrient in orange juice. One of the reasons for this is that consumers regard oranges as a good source of vitamin C. Some other fruits contain more vitamin C than oranges but few are as popular, see Table 2.4. The level of vitamin C in freshly extracted orange juice may vary a lot depending on orange variety and growing conditions.
2.2 Important properties of orange juice
TABLE 2.5 THE NUTRIENT COMPOSITION OF FRESHLY EXTRACTED ORANGE JUICE
Constituent Protein (total Nx6.25), g Amino nitrogen, g Fat (ether extract), g Soluble solids, total, g Sugar, total as invert, g Reducing sugar, g Sucrose, g Acid, total, g Malic acid, g Mineral nutrients as ash, g Calcium, mg Chlorine, mg Fluorine, mg Iron, mg Magnesium, mg Phosphorus, mg Potassium, mg Sodium, mg Sulphur, mg Ascorbic acid (vitamin C), mg Betain, mg Biotin, mg ß-Carotene, mg Choline, mg Flavonoids, mg Folic acid, mg Inositol, mg Niacin, mg Pantothenic acid, mg Pyridoxine (B6), mg Riboﬂavin (B4), mg Thiamine, B1, mg Vitamin B12, µg
Content per 100 g Range 0.58–1.29 0.029–0.07 0.0–0.66 8.1–17.7 6.23–14.3 2.25–8.83 2.98–6.24 0.58–1.73 0.10–0.17 0.27–0.70 6.3–29.4 3.6–13.2 0.11–0.19 0.1–0.8 9.8–17.1 8.0–30.0 116–265 0.2–2.4 3.5–11.3 26–84 41–47 0.0001–0.00037 0.23–0.28 7–15 80–118 0.003–0.007 170–210 0.13–0.46 0.06–0.3 0.023–0.094 0.013–0.059 0.057–0.106 0.0011–0.0012
Average 0.91 0.047 0.2 12.3 9.15 4.60 4.37 1.09 0.15 0.41 15 6 0.14 0.3 12 20 196 0.5 8 56.6 44 0.00024 0.12 11 99 0.004 194 0.26 0.13 0.038 0.021 0.077 0.0011
Source: adapted from Redd and Praschan.
Flavonoids and pectin are believed to be linked to the reduction of blood serum cholesterol in humans. The ﬂavonoid hesperidin can, however, cause problems during orange juice production as it precipitates out as white ﬂakes in the evaporator. A number of other nutrients like thiamine and potassium are also found in orange juice but not in larger amounts than found in other fruits and vegetables. A comprehensive list of nutrients in freshly extracted orange juice is given in Table 2.5.
Folic acid is also found in signiﬁcant amounts in orange juice. This B vitamin is required for DNA synthesis and its deﬁciency is ﬁrst expressed in tissues with high rates of cell turnover. Pregnant women are prone to folic acid deﬁciency which, in rare cases, may affect the foetus. Folic acid is quite heat-sensitive, but the vitamin C in citrus juice protects it from degradation during heat treatment.
2.3 Orange juice categories
Ready to drink NFC or direct juice
RTD juice made from concentrate
Fig. 2.3 Main orange juice categories.
For dilution FCOJ 41–52 °Brix
2.3.1 READY-TO-DRINK ORANGE JUICE
Ready-to-drink (RTD) orange juice is at the strength at which it will be consumed. It does not require dilution before drinking. Some categories of RTD orange juice are given below. Freshly squeezed orange juice
2.3 Orange juice categories
Juice packaged directly after extraction but without pasteurisation or any other physical or chemical treatment. Its shelf life is very short.
Quality parameters as deﬁned in product speciﬁcations and grade standards provide orange juice buyers and sellers with appropriate information about the product they are handling. This applies to any link in the production chain. To the consumer, however, orange juice covers a wide range of products, many of which are not well-deﬁned. Many different terms are used within orange juice marketing to describe the various products. Several of these terms are not consistent and have different meanings in different countries. Nevertheless, along with the increase in global trade and marketing of orange juice, there is growing pressure to harmonise the terms used. Orange juice products can be divided into two main categories – ready-to-drink juices and concentrates. The latter require dilution with water before consumption. Ready-to-drink juices are either NFC or reconstituted from concentrate.
Fresh orange juice
A misleading term that should be avoided. Sometimes it is used to mean freshly squeezed orange juice, in other markets it is used for juice distributed chilled (NFC or made from concentrate). Not-from-concentrate juice (NFC)
Juice which has neither undergone a concentration step nor dilution during production. This term originated in the USA. Premium juice
A term which has been used in the USA and Canada for NFC for marketing purposes. Direct juice
A term sometimes used in Europe for NFC. The expression “not from concentrate” is felt to imply to consumers that juice derived from concentrate is inferior to NFC. In European legislation NFC is deﬁned simply by the term fruit juice.
2.3 Orange juice categories
Pure juice or 100 % juice
Orange juice drinks
Often used on a label to deﬁne pure juice, being a direct juice or one made from concentrate to distinguish it from nectar.
Drinks with a lower juice content than nectars. They are not subject to juice legislation but to general food legislation. In some cases they may contain only peel oil and ﬂavouring agents.
Orange juice from concentrate
This product is also known as orange juice made with concentrate. The juice is produced by diluting orange concentrate with potable water.
Orange ﬂavour drinks
Products tasting of orange but containing no genuine juice product. 2.3.2 CONCENTRATED ORANGE JUICE
Concentrated orange juice is diluted to single strength before consumption. The most common orange concentrate products for the trade and retail sectors are given below.
FORTIFIED ORANGE JUICES
Juice with added ﬂoating pulp
This is juice with added ﬂoating cells (also known as pulp or fruit meat). The product is sometimes called Home style, Natural, etc. The added cells provide mouthfeel and increase the natural ﬁbre content of juice. Juice without ﬂoating cells is referred to as “smooth”.
Frozen concentrated orange juice (FCOJ), 65–66 °Brix
The standard product for traded orange juice concentrate. It is concentrated approx. 5.5 times. It is a bulk product only, stored and shipped at –6 to –25 °C. The term may be misleading as FCOJ at such high concentration does not freeze solid but is still pumpable.
Both naturally occurring vitamins and man-made vitamins can be added by packers to increase the nutritional value of orange juice. Calcium enriched
FCOJ at approx. 55 °Brix
Calcium compounds, which are soluble in juice, are added to juice by the packer to increase its nutritional value.
This product is often referred to as Dairy Pack. It is a bulk product only. It is 66 °Brix concentrate cut back (rediluted), e.g. with single-strength juice and pulp, to the required concentration. No further additions are needed at the juice packer apart from water dilution. This product is commonly used by dairies.
Addition of nutritional ﬁbre (normally not from oranges) to increase the health value of juice.
FCOJ at min. 41.8 °Brix
RTD ORANGE PRODUCTS WHICH MAY NOT BE CALLED ORANGE JUICE
A retail product, mainly in US, for dilution with water (3 times) to single strength at home, in restaurants, etc.
Orange juice with added sugar, acids and/or water. The minimum fruit content varies according to legislation. For orange nectar, EU regulations stipulate min. 50 % fruit juice content at RTD strength.
Concentrate at approx. 52 °Brix
A retail product aseptically packaged, mainly in Scandinavia. For dilution with water (4 times) to single strength at home, in restaurants, etc. It is distributed chilled or at ambient temperature.
2.4 Regulations governing juice origin
In the USA, standards governing the composition and labelling of food and the use of additives are under the administration of the Food and Drug Administration (FDA) and the United States Department of Agriculture (USDA). The standards for orange juice identity (or juice origin) are enforced by the FDA, whereas the standards for orange juice grades (more or less the quality) are enforced by the USDA. In the European Community, legislation covering fruit juices and fruit nectars is based on a Council Directive concerning fruit juices and similar products. The current directive 2001/112/EC came into force in 2001 and EU countries were given until 2003 to comply with it. The demands for labelling are outlined in the Council Directive on labelling, although speciﬁc labelling requirements are given in the fruit juice Council Directive. Countries in other regions have similar legislation to that of the US and EU. Countries not having their own legislation refer to the Codex Alimentarius published by the FAO. There is a general desire worldwide to harmonise orange juice standards to promote free and open global trading. This is an objective of the Juice Products Association (JPA), whose members are drawn from the United States, Canada, Mexico, Central and South America, and Europe. The JPA’s position is that the USDA standards covering the grade and quality of orange juice should be applicable throughout the major citrus juice producing countries. It even suggests that USDA standards should be adopted as a worldwide harmonised standard. There are ongoing discussions with European and other authorities on this topic. An overview of the most important aspects of legislation in the US, EU and other countries are found in Section 11, Standards and Regulations.
2.4 Regulations governing juice origin In the European Union and several other countries, the term ‘orange juice’ may only be used for juice extracted from sweet oranges, Citrus sinensis. In the USA, regulations allow for up to 10 % of tangerine or hybrid orange/tangerine juice to be included in orange juice. Also Codex Alimentarius allows for 10 % mandarine juice. These added juices can improve the colour and ﬂavour of the blended juice. In principle, regulations governing direct juice, or NFC, require that ﬂavour and pulp removed during processing should be added back to the same juice. For reconstituted orange juice, water should be added back to the minimum concentration deﬁned in the quality standard applied in a country. Essences should be added back to restore ﬂavours, and pulp may be added to achieve the desired properties of the ﬁnal juice product. Orange juice should come from the endocarp of the fruit and be extracted by mechanical means. The EU directives for fruit juices of 2001 allow pulp wash in orange juice from concentrate, but not in direct (NFC) juice. In-line addition of pulp wash is also allowed in the US (up to 5 %) and many other countries. Although attempts are being made continually to reach consensus between legislation in different global trading blocs, regulations governing fruit juices and other beverages still vary worldwide. In general, legislation covers: • product origin • how juice processing may be carried out • the composition and quality of fruit juices • product labelling
The supply chain and global consumption of orange juice
In section 3 you will read about: • How FCOJ is traded as a commodity product and the signiﬁcance of the futures market to bulk trading. • Import duties with examples in certain trading blocs and countries. • The amount of orange juice products consumed in major markets.
• The structure of the orange juice industry. • The evolving relationship between orange growers and fruit processors. • How marketing processors and bulk processors operate. • The activities of blending houses, juice packers and soft drink producers. • The ﬂuctuations in the worldwide pricing of bulk juice products.
3. The supply chain and global consumption of orange juice Pricing and trading Special terminals for handling frozen concentrate in bulk are located in major ports. The world market price of FCOJ ﬂuctuates according to its supply and demand. Freecarrier Rotterdam warehouse is a common standard for FCOJ (66 °Brix) traded prices, which include freight charges to the port of Rotterdam, the Netherlands. The futures market enables the citrus industry to manage commercial risks. It also sets a value for FCOJ. The speculative activity of the futures market provides the ﬁnance needed to transact commercial hedges and set price levels. In addition to long-term contracts there is also a spot market for FCOJ. Quite large differences in import duties for orange juice exist between importing countries. As regards the consumption of orange juice, the USA and Europe are the largest markets.
Summary Orange juice products usually change hands many times along the supply chain. It is thus important for all involved in the intermediate steps to be familiar with the total sequence of juice production. In Florida, orange growers are becoming diversiﬁed agribusiness companies. In Brazil, the large orange processors still get part of their fruit from their own groves. So-called marketing processors produce and sell their own juice brands. Bulk processors mainly sell their products in bulk form. Blending houses provide concentrate and bases of consistent quality according to deﬁned customer speciﬁcations. Juice packers treat bulk product as required and then pack it in consumer packages. Soft drink producers may use orange concentrate and prepared bases from blending houses as raw materials.
3.1 The chain of supply
There are many links in the chain of supply for orange juice – from ripe oranges ready for picking to the consumer opening a carton of juice at a distant location (see Figure 3.1). The product usually changes hands several times along the way. It is thus important to be familiar with the complete sequence of juice production in order to understand the commercial conditions for each type of company forming the intermediate links in the supply chain. This section refers generally to orange juice production in Florida and Brazil, which dominate the world juice market.
Full vertical integration – i.e. having all the steps from fruit harvesting to distribution of packaged consumer product under one roof – is rare in the orange juice industry. This has resulted not only from geographical factors but also from the way the industry has matured. There is a trend for each link in the production chain – growers, fruit processors, juice packers and retailers – to become independent businesses. This may be a natural consequence of the marketplace demanding increased and specialised competence at each step of the production sequence. It may also be partly due to commercial factors, such as long-term supply contracts and the futures market, that allow individual sectors of the citrus industry to reduce their own commercial risk from market price ﬂuctuations.
3.1 The chain of supply
Oranges Packaged juice – reconstituted and NFC
Packaged juice and juice drinks
Bulk concentrate and NFC
By-products Bulk concentrate and NFC
Still and carbonated soft drinks
Fig. 3.1 The supply chain from fruit harvest to consumers. Soft drink bases
Soft drink producers
The orange-growing and processing industry undergoes constant change in line with evolving commercial and political conditions. On the growers’ side, in Florida there has been a shift from independent farmers to diversiﬁed agribusiness companies that are active in marketing and interested in long-term business relationships. Moreover, in Florida during the 90’s, growers divested themselves of juice production, and processors who had until then owned their own groves instead formed partnerships with growers. Long-term agreements between processors and growers ensure the stable supply of raw materials. There are several organisations promoting the interests of Florida citrus growers to give them a stronger marketing and negotiating position than their counterparts in other countries. In Brazil, the large orange processors still get part of their fruit (20 %) from their own groves. The remaining fruit is mostly obtained by long-term contracts with medium- and largesize growers.
Orange growers manage the groves, harvest and sell the orange fruit. They are organised in many ways – from small independent growers selling their fruit to a fruit handler or through a cooperative, to growers who are part of a large fruit processing company. For the fruit processor it is essential to secure a continuous supply of oranges in sufﬁcient quantities and at the right price. Traditionally, many orange processors have owned the groves needed to supply them with all or the majority of fruit required throughout a season. This is particularly important during periods of uncertain fruit supply and unstable prices, e.g. as was experienced during the Florida freezes in the 1980’s. Today, however, the supply of fruit is abundant in most regions, although the drop in concentrate prices has made alternative outlets for fruit more interesting than concentrate production.
3.1 The chain of supply
The largest marketing processors are based in Florida, such as Tropicana, the leading NFC producer, and Citrus World. They process fruit into juice and ﬁll it into retail packages at their own facilities. They also purchase additional juice in bulk form from other bulk processors. For marketing processors, the control of product availability is regarded as more important than ownership of manufacturing assets. As an example, Coca-Cola now focuses on marketing and distributing Minute-Maid brands, while the production facilities are owned and operated by a Brazilian bulk processor, Cutrale. The majority of orange juice worldwide is produced by bulk processors. Bulk delivery is most important to the large Brazilian processors. They do not possess their own consumer brands, one reason being to avoid competing with their bulk juice customers. Several joint ventures have been created for the rapidly growing NFC market in South America. Brazilian bulk processors pack retail products at their facilities as co-packers for companies that have their own branded products and distribution and marketing chains. The bulk products are transported in ship tankers, tank cars or in individual containers, such as 200 litre (55 gallon) steel drums and one tonne bagin-box containers. Efﬁcient transport is crucial for these commodity products. (See also Section 6.) Several terminal installations around the world are dedicated to receiving and shipping frozen concentrated orange juice (FCOJ) using tankers. The larger Brazilian processors own terminals in Brazil for exporting bulk products from Brazil, and in Europe, the USA and Japan for importing FCOJ into these markets. These companies also own several large tanker ships designed and dedicated to transporting FCOJ. Recently, bulk ships and terminals dedicated to handling chilled aseptic NFC from Brazil have also come into operation. Bulk processors make their money from the difference in bulk concentrate prices and fruit prices – the bulk processing margin. Florida bulk processors are very vulnerable to the wide ﬂuctuations in FCOJ prices.
Fig. 3.2 The supply of oranges to fruit processors. How growers are paid
Fruit quantities are often quoted in “ﬁeld box” units. Based on Florida practice, one box is deﬁned as 90 lb (40.8 kg) of oranges. In Florida, payment to growers is not based on the weight of delivered fruit but on the amount of soluble solids (juice sugars) obtained from the fruit. The quantity of soluble solids is calculated from the volume of juice extracted from the fruit multiplied by the °Brix level of the juice. The amount of extracted juice is determined by squeezing a sample of oranges on a “State test extractor”. Oranges rejected during screening at the processing plant fruit reception area are not paid for. In Brazil, payment to the growers was made traditionally according to the gross weight of delivered fruit, including rejects. Payment today is still based on fruit quantity although the contract format has changed. Standard contracts with payment to growers based on FCOJ world market prices were abandoned in the mid 90’s and replaced by free negotiations. 3.1.2 TYPES OF FRUIT PROCESSOR
In short, orange processors take in fruit and process it to produce concentrate and NFC. They can be divided into two groups: • marketing processors • bulk processors Marketing processors sell packaged juice under their own brand name, which requires retail and consumer marketing skills. Bulk processors mainly sell their products in bulk form, which requires skills in the efﬁcient distribution and marketing of a commodity.
3.1 The chain of supply
Bulk processors Long-term contracts
Juice packers Long-term contracts
Fig. 3.3 The orange juice supply chain from bulk processors.
Therefore they need to take advantage of the commodity trading market (and to beneﬁt from its commercial protection) in a similar way to their Brazilian counterparts. The links between Florida and Brazil strengthened during the 1990’s. The major Brazilian bulk processors acquired several juice facilities in Florida and operate 8 plants (2002) contributing to about half of Florida’s juice production. Operating in both markets offers beneﬁts such as higher trading efﬁciency and balancing concentrate quality. NFC, which has had a high growth rate in Florida and now accounts for more than a 40 % share there, offers better margins than FCOJ for Florida juice producers. Bulk processors supply NFC to juice packers and marketing processors but some also co-pack in their own facilities. The links between Florida and Brazil strengthened during the 1990’s. The major Brazilian bulk processors acquired several juice facilities in Florida and operate 8 plants (2002) contributing to about half of Florida’s juice production. Operating in both markets offers beneﬁts in trading efﬁciency and balancing concentrate quality. The different routes that orange juice products take from bulk suppliers are shown in Figure 3.3.
season and operating conditions change in the plant. Juice packers, however, need to buy raw juice of deﬁned quality as they, in turn, need to supply the market with uniform products over the long term. The need for consistent juice quality has created the industry segment “blending houses”. Although they normally work with many different fruit juices, orange juice is a primary product for blending houses. Their purpose is to provide juice packers with a concentrate (and sometimes also NFC) that consistently meets deﬁned quality speciﬁcations. They achieve this by blending concentrates of different origin and adding ﬂavour fractions, often according to customer-speciﬁc recipes. In addition to supplying the deﬁned juice product, blending houses normally have specialist product know-how which is made available to their customers. (Blending house operations are also discussed in Section 6.) Blending houses are often located in or near the main ports receiving juice concentrates. The larger Brazilian processors who have their own terminal facilities also offer blending house operations. The preparation of soft drink bases is another important business activity of those blending houses which have developed from ﬂavour-manufacturing operations. Purchasing concentrate from a blending house is generally more expensive than buying it on the spot market. However, the buyer can be assured of product quality meeting his demands.
3.1.3 BLENDING HOUSES
Consistent quality between batches of FCOJ cannot be maintained during processing. Variations in ﬂavour proﬁle, Brix:acid ratio, pulp levels, etc., are unavoidable because fruit varies during the
3.1 The 3.1 chain The ofchain supply of supply
Fig. 3.4 World market for FCOJ (Brazilian export prices Rotterdam) Source: Foodnews
Fluctuations in world market prices for FCOJ, not always reﬂected in retail prices, put pressure on juice packers. For a successful operation, the juice packer requires important skills in several areas:
3.1.4 JUICE PACKERS
Juice packers take in bulk product, treat it as required and then pack the product in consumer packages. The juice packer may also control the distribution of the packaged product. Juice packer operations are described in more detail in Section 7. As with fruit processors, there are two main categories of juice packer – those who market their own brands and those who focus on copacking, e.g. for private label brands. There are dedicated juice packers and dairies with juice packing operations. The product range of juice packers may include nectars and fruit-based still drinks in addition to 100 % pure juices.
Sourcing: raw material costs constitute a major share of the total costs. The right juice quality and favourable contracts are vital to overall proﬁtability. Processing/Packaging: where the focus is on maintaining product quality and keeping running costs, including product losses, low. Distribution: distribution of packaged product also accounts for a signiﬁcant share of the total costs, and efﬁcient distribution therefore plays an important part in overall proﬁtability.
packers treat bulk “Juice product as required and
Marketing: marketing skills are important to both packers who market their own brands and those who focus on co-packing.
then pack the product in consumer packages
3.2 World market pricing for bulk juice products
In the mid 1990’s world market prices for FCOJ (66 °Brix) were quite stable around 1,500–1,600 USD/tonne CIF Rotterdam because of efforts made by the Brazilian export association, ABE. However, new producers entering the market and large FCOJ stocks remaining after a cold European summer led again to a slump in prices, as low as 700 USD/ tonne. In the early 2000’s price levels remained around 1,000–1,200 USD/tonne. Although these levels are claimed to be near or below break-even for most juice processors, the purchasing market did not allow increases in price levels. Brazil is the dominant world exporter of frozen concentrate and Europe the largest market, with import harbours in Belgium and the Netherlands. Rotterdam is a commonly used reference for FCOJ world market prices. Freecarrier warehouse means that the price includes freight charges to the port of Rotterdam in the Netherlands, and loading product, e.g. on road tankers. But import duty and transport costs from the tank farm to the user need to be added. Price levels for Florida FCOJ are given in a different unit, US dollar per pounds solid, which is quoted free on-board carrier in Florida. Hence the bulk price does not include overseas transport, but this is not normally required as the main market is North America. FCOJ world market prices are set in US dollars. Variations in the Brazilian currency against the US currency inﬂuence the Brazilian processors’ margins. For European markets, the exchange rate of the Euro against the US dollar will inﬂuence retail juice prices. As regards the market for juice supply, the extensive planting of new trees seems to assure an adequate supply of fruit and orange juice concentrate in the foreseeable future. Nevertheless, a reduction in Brazilian output due to adverse climate effects or diseases can alter this outlook.
3.1.5 SOFT DRINK PRODUCERS
Although the term soft drinks strictly means all non-alcoholic drinks, the name soft drink producers is commonly applied to manufacturers of retail packaged carbonated beverages and fruitﬂavoured still drinks. The soft drink producer may use orange concentrate as a raw material, but often he purchases a prepared base from a blending house. For drinks of low fruit content, the ﬂavour of FCOJ is not strong enough and so it has to be enhanced with additional ﬂavours. Other ingredients in the soft drink base may be emulsiﬁers and preservatives. At the soft drink producer, only sugar, acid and water (plus carbonation as required) need to be added to a ready-prepared base. A few large multinational companies and many local companies can be found among the soft drink producers. As with juice packers, blending house specialists may provide a valuable source of experience and product knowledge for small to medium-sized soft drink producers. Blending houses may also help in developing new soft drink products and in responding to new consumer trends.
3.2 World market pricing for bulk juice products World market prices for FCOJ have shown wide ﬂuctuations over the years. Prices increased during the 1980’s as freezes in Florida reduced orange supplies. Prices dropped between 1992 and 1994 as large harvests were again recorded in Florida. In the autumn of 1994 a severe drought in Brazil once more led to sharply rising prices for frozen concentrate. (See Figure 3.4.) In general there is a correlation between FCOJ price levels and expected supply, but in the past over reaction by the market has resulted in very wide price ﬂuctuations. This usually constitutes an undesirable situation for both suppliers and juice purchasers.
3.3 FCOJ commodity trading and the futures market
3.3 FCOJ commodity trading and the futures market
UNITS USED FOR BULK JUICE TRADING
The buying and selling of FCOJ have evolved into commodity trading. Two of the largest Brazilian bulk juice producers, Louis Dreyfus and Cargill (both also producing in the USA), are major commodity trading companies active in several other ﬁelds besides citrus. They have inﬂuenced the trading of citrus on the commodity trade market. Commodity products, which are usually supplied in well-deﬁned units, can be traded on the “futures” market. “Futures” are contracts agreed for the future delivery of a physical commodity, such as FCOJ. Cash price is the price at which the actual commodity is selling for.
On the world market, frozen concentrates of Brazilian and other origin are usually traded per metric tonne product, with prices given as USD/tonne concentrate. In the USA, however, the basic unit for pricing orange fruit, singlestrength juice and FCOJ is the content of soluble solids (in principle the sugars), not the weight or volume of product. The unit used is lb. soluble solids. The US futures market also use lb. soluble solids to deﬁne product quantity. The following approximate factors can be used when converting prices: For FCOJ of 66 °Bx 1000 USD/t conc. 1430 USD/t conc.
Risk management and price setting
0.70 USD/lb solids 1.0 USD/lb solids
For NFC juice of 11.8 °Bx 1000 USD/t juice 3.82 USD/lb solids 260 USD/t juice 1.0 USD/lb solids
The futures market provides a means of managing risk for the citrus industry, a way for all involved to hedge (protect against ﬁnancial loss) their risk exposure caused by ﬂuctuations in cash prices for products. Futures markets require the participation of both hedgers (risk shifters) and speculators (risk assumers). Hedgers are those in the citrus industry, such as fruit processors and sellers, who transfer unwanted risks associated with their normal commercial activities. Speculators (nonproducers/processors) seek ﬁnancial gain by cor rectly predicting changes in future price moves. The speculative activity provides the ﬁnance required to carry out commercial hedges. In addition to risk shifting, the futures markets also sets the value for one pound of FCOJ solids, known as price discovery.
Trading of FCOJ futures takes place through the Citrus Associates of the New York Cotton Exchange, NYCE. This nonproﬁt organisation provides the physical location where FCOJ futures and options are traded (by voice and hand signals), and oversees the regulations governing all transactions. It forms part of New York Board of Trade, NYBOT. The regulations deﬁne quantities of FCOJ to be contracted and the time periods allowed for trade and delivery of contracts (every other month). Grade standards for product quality, as well as product identiﬁcation and inspection, are also speciﬁed in the regulations.
3.4 Import duties and juice imports
In 2004, a new form of futures contract was introduced that recognised the Florida/Brazil origin of FCOJ in order to more correctly follow cash market transactions, which tend to value FCOJ from Florida and Brazil differently to that of other origins. The futures market is important to the citrus industry, not only as a tool for risk management but also as a price basis for purchasing fruit and for sales contracts for bulk concentrate. The NYCE provides hedging opportunites for citrus industry players active in Florida, but there is no similar futures exchange providing risk management in São Paulo. The proﬁt of bulk juice processors comes from the price difference between the fruit and concentrate. Therefore they must posses good skills in marketing a commodity product and risk management. In addition to long-term sales contracts there is also a spot market for FCOJ, delivered from tank storage and in drums. Trade on the spot market is high when price levels are unstable. Products on the spot market may be of less well-deﬁned quality or product speciﬁcations and thus command lower prices. During periods of depressed retail prices for orange juice, juice packers may be forced to acquire large volumes of such juice on the spot market.
3.4 Import duties and juice imports There have been long-lasting negotiations between trading blocs aimed at reducing trade barriers and promoting freer trade, including that of citrus products. Examples are the GATT (General Agreement on Trade and Tariffs) where major agricultural agreements were established in the Uruguay round of talks held in 1994. The North American Free-Trade agreement, NAFTA, intended to reduce trade barriers between USA, Canada and Mexico was reached in 1994. Work on a similar agreement to also include all countries in South and Latin America, Free-Trade Area of the Americas or FTAA, was initiated in 1998. Although scheduled to come into force in 2005, the participants are still discussing many issues involved with the agreement. Since both Brazil and Florida, the major orange juice regions, are part of the FTAA, the agreement would have a signiﬁcant impact on orange juice trade. The Florida citrus industry are carefully evaluating the likely impact on Florida orange growers and the juice market.
SOME TERMS USED WITH TRADE TARIFFS Ad Valorem tariffs: duty calculated as a percentage of the value of the imported product. Freight costs are included in the product value. Speciﬁc tariffs: a duty of a ﬁxed amount of money per unit of juice independent of the value of the product. Quota: deﬁned maximum quantity of product which is allowed, e.g. at a lower import duty. SSE or single-strength equivalent: FCOJ calculated as the volume of juice it would yield when reconstituted to single-strength juice. GATT: General Agreement on Trade and Tariffs. NAFTA: North American Free Trade Agreement.
3.4 Import duties and juice imports
2500 2000 1500 Others
Fig. 3.5 The major juice import markets. Source: FAO
For orange juice, there are quite large differences in import duties between the various importing countries. Duties often depend on the exporting country, for example, several exporting countries have agreements with respective importing markets which enable duty-free or reduced import tariff. In general, however, such agreements do not apply to the major exporters, Brazil and the USA. The US “duty drawback” procedure favours the export of juice from the US. In the duty drawback system juice exporters/importers can recover the import duty paid for a certain volume of juice if they export the same volume and kind of product. US import duties distinguish between
FCOJ and NFC. Tariffs are higher for FCOJ than NFC (calculated as single-strength juice.) In general, citrus growers and fruit processors receive little or no subsidies. Within the EU, however, signiﬁcant subsidies are paid to orange processors who purchase fruit from EU fruit growers at the minimum recommended fruit prices. The European Union is the largest juice import market, followed by the USA. The relative sizes of the major juice import markets are shown in Figure 3.5. The consumption of packaged orange juice per region is shown in Figure 3.6.
Fig. 3.6 Consumption of packaged orange juice in certain regions, 2003. Source: Euromonitor
3.4 Import duties and juice imports
• Mexico Phasing down to duty-free unlimited import by 2008 (NAFTA agreement) For 2003: – within quota for FCOJ, 4.6 USD/100 l SSE – within quota for NFC, 1.8 USD/100 l SSE • Most Favoured Nation (e.g. Brazil) FCOJ 7.9 USD/100 l SSE NFC 4.5 USD/100 l SSE
3.4.1 IMPORT DUTIES WITH SOME TYPICAL EXAMPLES European Union
Tariffs for orange juice imported into the European Union vary greatly depending on the exporting country. The dominant share of juice imported into Europe comes from Brazil and is subject to import duty for Most Favoured Nation (MFN). This duty, which was 20 %, has gradually been lowered under GATT, and is differentiated according to the degree of concentration and temperature. EU import duties are ad valorem (a ﬁxed percentage of the product value including freight). Some import tariffs in effect in 2002 are presented in the list below: • From EU countries and some non-EU Mediterranean countries, 0 % • Mediterranean Basin Preference (mainly Israel and Morocco) – within quota, 2.3 % – exceeding quota, 5.7 % • Lomé convention countries, 0 % (African, Caribbean incl. Belize and Costa Rica, Paciﬁc) • Most Favourable Nation (MFN) tariff (applies to countries such as Brazil and USA) – FCOJ at -18 °C, 15.2 % – FCOJ at -10 °C, 12.2 % • Mexico – within quota for FCOJ, 3.8 % – exceeding quota imported at MFN tariff
The USA implements a “duty drawback” procedure. This allows US importers of FCOJ who also export FCOJ or reconstituted orange juice to be reimbursed 99 % of the import duty paid on the same quantity of imported concentrate as was exported within a 3-year period. NFC exports are not eligible for drawback against imported FCOJ. Canada
Canada allows orange juice concentrate to enter duty-free but levies import duty on singlestrength juice. All juice imports from NAFTA countries (USA and Mexico) are tariff-free. Japan
Until 1979 there was little fruit juice import into Japan due to very low import quotas. The quotas were gradually increased until they were removed altogether in 1992. Import duties are ad valorem. • Most Favoured Nation tariff FCOJ, 25.5 % Republic of Korea
Until 1989 juice imports were restricted by very low quota. Following GATT agreement, quotas for orange juice imports were removed in 1997. • Most Favoured Nation tariff for FCOJ and juice ad valorem, 55 %
Import duties are speciﬁc in the USA. The rates, differentiated for FCOJ and NFC, are given as a ﬁxed fee per pound of soluble solids. Some of the current duties, converted to US dollars per 100 litres single-strength juice, are given in the list below. Most US juice imports are as FCOJ and the largest exporter is Brazil, which is subject to full MFN duty. • Caribbean Basin Initiative beneﬁciary countries (e.g. Belize, Honduras, Costa Rica), 0 % • Israel (as of 1995), 0 %
Following China’s WTO entry, tariffs for imported orange juice have decreased signiﬁcantly. Tariffs are ad valorem: • Frozen juice Most Favoured Nation tariff, 7.5 % • Nonfrozen single-strength juice MFN, 32 %
3.5 Global orange juice consumption
Austria Belgium Denmark Finland France Germany Greece Ireland Italy Netherlands Norway Spain Sweden Switzerland UK Canada Brazil China South Korea
Fig. 3.7 Consumption of packaged orange juice in European and other countries, 2003. Source: Euromonitor
has gradually increased to take more than 40 % market share. RTD juice made from concentrate accounts for about 40 %. Virtually all RTD orange juice in the US is distributed refrigerated (4 °C). See also section 10.3. In Europe, nearly all retail orange juice is RTD, there is very little concentrate. The total orange juice volume for Western Europe in 2000 was about 3 billion litres. European consumption has had a high growth rate – almost doubling between 1983 and 1993 – but since then growth has slowed down to about 3 % annually. Most orange juice in Europe is made from concentrate. The consumption of NFC has increased over the last decade and now accounts for more than 10 % of total orange juice sales. The growth in per capita income and the perception of NFC quality as being similar to that of fresh fruit have driven the increase in NFC sales despite its high price premium.
3.5 Global orange juice consumption North American and European markets are the largest consumers of orange juice. The USA and Canada account for some 50 % of total global consumption of packaged orange juice, whereas Western Europe consumes about 30 % of the total volume. (See Figure 3.6.) In the USA, consumption of orange juice, about 5 billion litres/year in 2001, has remained fairly constant over the past decade. Nevertheless, there has been a constant shift in market share for the three main types of orange juice in the US market: frozen concentrate for home dilution, ready-to-drink (RTD) juice made from concentrate, and NFC. Frozen concentrate has steadily decreased from a dominant position to less than 15 % of total orange juice retail sales. NFC, which emerged on the US orange juice market in the mid-80’s,
3.5 Global orange juice consumption
Litres / capita/year
20 15 16.6 10 13.8 5
Fig. 3.8 Per capita consumption of orange juice in some countries, 2002. Source: Canadean
NFC is retailed at up to double the price of orange juice made from concetrate. Compared with FCOJ, the 5–6 times larger storage and shipping volumes for NFC combined with the stricter quality demand on raw fruit for NFC result in a signiﬁcantly higher cost for bulk NFC imported into Europe. During the introduction of NFC in Europe the market was dominated by Florida juice, but today NFC is often a blend of origins. In other markets, a rapid growth in the consumption of packaged orange juice is noteworthy in South America, particularly Brazil. Some Far East markets such as Japan and the Republic of Korea have also shown large growth rates, although these may ﬂuctuate from year to year due to economic factors. Large cities in the coastal region of China constitute an area with high economic growth and a rapidly growing demand for orange juice. Eastern European counties are also rapidly expanding markets The consumption of packaged orange juice in European and other countries is shown in Figure 3.7.
3.5.1 PER CAPITA ORANGE JUICE CONSUMPTION
The USA is not only the largest total consumer of orange juice worldwide, but it also has the highest consumption per capita, some 16 l (4.2 US gal.) per person per year. Per capita consumption in the UK comes second, where orange juice accounts for the highest share of all fruit juice with more than 70 % of the market. Although Germany has the highest total fruit juice consumption in Europe, because apple and blends dominate, the per capita orange juice consumption is much lower than in the UK. The per capita estimates in Figure 3.8 are based on data collected by market organisations and refer to 100 % orange juice. The Florida Department of Citrus (FDOC) also estimates the overall orange juice utilisation in major markets. This is the “presumed consumption”, which is based on so-called “disappearance data”, or net utilisation of bulk orange concentrate and NFC. This means that orange concentrate used to produce nectars and fruit drinks is also counted as orange juice consumption. The values presented by the FDOC are therefore higher than the actual consumption of 100 % juice only. However, they provide a valuable understanding of the total usage of processed orange juice in different markets.
3.5 Global orange juice consumption
Principles of processing orange juice
In section 4 you will read about: • How the different steps of juice processing and bulk storage affect the quality of orange juice. • How oxygen gets into juice and its role in degrading juice quality and causing problems during operation. The removal of oxygen from juice is also discussed.
• Which microorganisms cause juice spoilage and the inﬂuence of raw materials and cleaning procedure on product contamination. • Why and when pasteurisation is carried out and the conditions needed for effective heat treatment.
4. Principles of processing orange juice Summary A good understanding of the properties of orange juice is required to design and operate processing plants that maintain high juice quality. The properties of fresh fruit and the initial processing conditions (during juice extraction) inﬂuence the quality of the end product. Heat treatment of juice is essential for obtaining the desired product shelf life, but the process should be designed to minimise unwanted quality degradation. Bulk storage conditions that minimise changes in quality are essential because juice may be stored for a year or more.
packages. It is therefore essential to prevent air from entering product streams, and to remove it before ﬁlling and packaging. Orange juice is a high-acid product which limits microbial growth to acidtolerant bacteria, yeasts and moulds. Yeast fermentation is the prime cause of microbial spoilage in aseptically packaged juice. Effective cleaning procedures are essential in controlling microbial contamination. Pasteurisation of orange juice is necessary for inactivating enzymes and for destroying microorganisms capable of growing during storage. Enzyme activity leads to cloud loss in single-strength juice and gelation in orange juice concentrate. The relevant enzymes in orange juice require a higher heat load to be inactivated than that for microorganisms.
Minimising loss of quality Air in juice leads to reduced product quality, foam during deaeration and ﬁlling, and uneven distribution of ﬂoating pulp (if any) in
Raw materials Quality Treatment
Processing Heat treatment Oxygen
Bulk storage Temperature Time
Packaging Barriers Hygiene
Shelf storage Temperature Time
Fig. 4.1 Factors which inﬂuence juice quality.
into consideration in designing and operating a process plant. It should be stressed that, despite the long experience of the industry in processing orange fruit and the large amount of research that has been done on the subject, all the secrets of orange juice have not yet been revealed. This subsection takes a look at the impact of raw materials, processing and bulk storage on the quality of orange juice according to Figure 4.1. Considerations involved in minimising quality degradation during processing are listed in Table 4.1. The effect of packaging and shelf storage on juice quality is discussed in Section 9.
4.1 Impact of processing on juice quality Orange juice is a complex product. Therefore a good understanding of the basic nature and properties of orange juice is needed for processing and packaging orange juice. In fact, to ensure that high product quality is maintained during juice processing, such understanding is indispensable. Section 4 as a whole looks at the principles of processing orange juice that have to be taken
4.1 Impact of processing on juice quality
Highly alkaline water may affect the acidity of the ﬁnal product, and excessive solids and minerals will cause a brackish or metallic taste. Chlorine imparts water with a “pharmaceutical” taste and has a negative inﬂuence on juice colour and taste. Both iron and copper catalyse oxidation reactions which result in chemical changes. Microorganisms and organic debris contaminate juice, affect its taste and reduce product shelf life. However, the main spoilage organisms of juice products are not commonly found in water. Despite all the possible effects on juice quality, there are no regulatory standards specifying water quality for beverage production other than that it should fulﬁl the drinking water standards in the respective country. Read more about water treatment in subsection 7.3.
4.1.1 RAW MATERIALS Orange fruit
The quality of orange fruit is important for the characteristics of the ﬁnal orange juice product. Since oranges are natural products, they vary signiﬁcantly in ﬂavour, vitamin C content and colour according to the variety of orange, the time of season when harvested and the region of the world where they are grown. A prerequisite for initial high juice quality is the use of whole, undamaged oranges with low microbial populations. Juice concentrate
Juice concentrate is the raw material for the juice packer. As the quality of reconstituted juice depends very much on the quality of concentrate used, it is essential that high quality concentrate with the desired Brix:acid ratio, colour and sinking pulp content is used. °Brix determines the volume of single-strength juice that can be reconstituted from a given volume of concentrate. The microbial condition of concentrate is another important factor because high microbial loads demand more intensive pasteurisation to achieve the required product stability. The maximum microbial load in concentrate should be speciﬁed by the concentrate producer.
Processing steps to stabilise extracted orange juice with respect to enzyme and microbial activity are indispensable before concentration, bulk storage, packaging and distribution. One exception is perhaps for the small amount of freshly squeezed, unpasteurised single-strength orange juice which is distributed chilled and has a shelf life of up to 3 weeks, often shorter. Heat treatment with respect to time/temperature settings should be designed to minimise unwanted chemical and ﬂavour changes in the product. Never theless it should still give an adequate safety margin concerning the inactivation of enzymes and spoilage microorganisms.
Water must often be treated before it can be used for juice reconstitution. The degree of treatment depends on the water source. As regards reconstituted orange juice, the quality of water is critical with respect to the content of chlorine, metals, nitrates, salts, air, etc.
4.1 Impact of processing on juice quality
loss of nutritional value. It is generally agreed that the degradation of vitamin C in citrus juices can occur through both aerobic (depending on oxygen) and anaerobic (not depending on oxygen) reactions of nonenzymatic nature. Which one predominates depends on the temperature and availability of oxygen. During processing, the aerobic degradation of vitamin C predominates, whereas during orange juice storage both pathways must be taken into account. In the aerobic degradation of vitamin C, the presence of 1 mg oxygen corresponds theoretically to a loss of 11 mg vitamin C. This calculation is based on the reaction where vitamin C is oxidised to dehydroascorbic acid.
TABLE 4.1 PROCESSING CONSIDERATIONS AT THE FRUIT PROCESSOR - Choice of orange fruit. - Short residence time in the fruit bins before extraction to prevent deterioration of fruit. - Fruit washing and grading. - Fruit sizing. - Optimal extractor pressure and correct ﬁnisher settings to avoid unwanted (of ten bitter) compounds in fruit from entering the juice. - Evaporation using low temperature and short residence time to obtain high-quality concentrate.
AT THE JUICE PACKER - Preventing air contact during concentrate handling and reconstitution. - Water quality. - Short residence time after juice reconstitution and prior to pasteurisation to minimise microbial growth and vitamin C degradation. - The use of correct temperatures during pasteurisation and ﬁlling. - Package integrity. - Storage conditions.
AA + 1/2 O2
DHA + H2O
AA = ascorbic acid (vitamin C) DHA = dehydroascorbic acid
Oxygen is soluble in single-strength juice up to a level of approximately 8 mg/l, which corresponds to a potential loss of 88 mg vitamin C. Assuming an initial vitamin C content of about 450 mg/l, this corresponds to a 20 % loss in the nutritional quality attributed to vitamin C. Subsection 9.2.1 gives more information on how different storage conditions affect vitamin C degradation.
To a great extent the loss of quality during processing is similar to that encountered during packaging and shelf storage. Refer to Section 9, packaging and storage of orange juice, which complements the information presented in this section. Oxygen impact on vitamin C degradation
At the fruit processor, the loss of vitamin C (ascorbic acid) from orange fruit to frozen orange juice concentrate is generally negligible when the right processing conditions and short residence times before concentration and freezing are used. During reconstitution of the orange juice and further processing steps, the amount of oxygen present has an important impact on juice quality. Oxygen is a very reactive element which can induce several changes in the chemical composition of orange juice, the most dominant of which is the loss of vitamin C and consequent
The desirable taste of freshly squeezed orange juice is easily affected by heat treatment and subsequent bulk storage. The juice may undergo several chemical reactions that can degrade the original volatile ﬂavours of the juice. In addition, off-ﬂavours can be formed mainly from compounds in the aqueous juice matrix. The Maillard reaction, a well-known reaction between sugars (or vitamin C) and amino acids, is an example of this.
4.1 Impact of processing on juice quality
Several potential off-ﬂavour molecules have been identiﬁed in orange juice. Most of these compounds are formed during juice storage, although it takes a long time (several months) or storage at high temperature before any off-taste is noted, i.e. the compounds responsible for an off-taste are present in high enough concentration. PVG, 4-vinyl guaiacol, is an exception. This compound has been found in concentrations above its perception threshold in newly extracted and processed juice. It imparts an old fruit or rotten fruit aroma to the juice. PVG is formed from an odourless compound – ferrulic acid – normally present in juice. The concentration of free ferulic acid in juice has been shown to double after the ﬁrst pasteurisation step, thereby greatly increasing the possibility of PVG forming. More about off-ﬂavours is presented in subsection 9.2.3. When orange juice is concentrated in an evaporator, the volatile water-soluble and oil-soluble components that provide most of the characteristic orange ﬂavour are removed. The process ﬂavour (also known as “pumpout” ﬂavour) obtained is a combination of the loss of volatile ﬂavour and the cooked taste resulting from heat treatment. The impact of these unwanted changes can be compensated for by addition of ﬂavour fractions at a later processing stage.
For long-term storage, the lower temperatures are used. Industry experience has shown that this temperature range is needed to avoid changes in colour and taste. At temperatures below –20 °C, concentrate can be stored for several years and still be of acceptable quality. If the pasteurisation of juice prior to concentration has not been carried out correctly, the residual enzyme activity can lead to gelation of the concentrate. Pectic substances in the juice form a gel which prevents the concentrate from being reconstituted to a juice of acceptable quality. See subsection 4.4.2.
enzymes are not completely “Ifinactivated, gelation of concentrate may occur
Not-from-concentrate juice, NFC
Two kinds of bulk storage are practised for NFC: • frozen (in 200 l drums at –18 °C or lower) • chilled (in large aseptic tanks or aseptic bagin-box containers at –1 to 1 °C) Both forms of storage give a shelf life of at least one year. This long shelf life is necessary since juice from fruit harvested at different times of the season is blended to obtain consistent quality yearround. Low-temperature storage is important; a temperature around 0 °C is low enough to avoid deterioration of the juice while still keeping the juice as a liquid. An advantage of aseptic NFC storage over frozen NFC is that the juice does not have to be thawed before ﬁnal packaging. This avoids the use of crushing equipment and high energy input for quick thawing. At ambient temperature thawing takes several days and therefore product quality may deteriorate during this period due to microbial growth and ﬂavour degradation.
4.1.3 IMPACT OF LONG-TERM BULK STORAGE
During bulk storage the product is kept under conditions that minimise changes in quality. This is of great importance since storage may be for a year or longer. Demands on the storage conditions depend on the orange juice product, FCOJ and NFC, and the intended storage time. Frozen concentrated orange juice, FCOJ
Orange juice concentrate is bulk-stored frozen at temperatures from –6 to –25 °C to avoid degradation of product quality. A temperature of –8 °C is often used during bulk transport.
4.2 Air/oxygen in the product
4.2 Air/oxygen in the product
Air consists mainly of the gases nitrogen and oxygen. These gases are soluble in orange juice to a certain degree, but if the juice contains more air than it can dissolve, free or dispersed air bubbles are formed. Air in the product can cause a number of problems for the juice packer, such as: • decreased product quality due to oxidation • foam formation in the deaerator • foam formation during ﬁlling, which leads to underﬁlling of retail packages • uneven distribution of ﬂoating cells in retail packages
Fig. 4.2 The effect of temperature, pressure and sugar concentration on oxygen solubility.
The solubility of oxygen is important since dissolved oxygen is more difﬁcult to remove than dispersed oxygen. The solubility of oxygen and other gases in a liquid, i.e. the concentration of dissolved gas, depends on pressure, temperature and the concentration of soluble solids in the liquid (see Figures 4.2 and 4.3). Solubility decreases with: • increasing temperature • decreasing oxygen partial pressure • increasing concentration of soluble solids (sugars)
COMPOSITION OF AIR: Nitrogen N2 Oxygen O2 Other gases
Solubility of oxygen
78 % v/v 21 % v/v minor
It is therefore important to prevent air from entering juice during reconstitution and blending of concentrate. If the juice does contain air after reconstitution, it can be removed later in the process. Dispersed air can be decreased by letting the juice rest for half an hour in an open tank before pasteurisation. A deaerator can be used to further decrease the air content. A deaerator uses vacuum at ambient or elevated temperatures to remove dispersed and soluble gases from the juice. Nitrogen can be considered as an inert gas with regard to juice quality, whereas oxygen is very reactive and is involved in many reactions that impair quality. It is therefore essential to remove oxygen from juice. The deaeration efﬁciency is determined by measuring oxygen concentration in the product before and after deaeration.
The measured amount of oxygen in orange juice can sometimes be higher than its theoretical solubility values. This can be explained by the phenomena whereby free oxygen adsorbs as gas bubbles to pulp particles in the juice. When solubility decreases due to increased temperature and/or reduced pressure, the gas released does not leave the product but stays as gas bubbles on the surface of fruit cell particles. This adsorption phenomena appears mainly on large particles in the form of added ﬂoating cells, but not on the smaller sinking pulp particles.
4.2 Air/oxygen in the product
4.2.1 SOURCES OF AIR/OXYGEN 100 kPa, atmospheric pressure
12.00 10.00 8.00 6.00 4.00
2.00 0.00 0
Fig. 4.3 Solubility of oxygen in water as a function of temperature at two different pressures.
The main reason for deaerating juice is to reduce its oxygen concentration. Oxygen is very reactive and promotes many of the reactions that take place in juice during processing and storage which lead to quality degradation. The most important reaction is the oxidation of vitamin C, which leads to loss of nutritional quality (see subsections 4.1 and 9.2). Considering that many countries have regulations that deﬁne the minimum level of vitamin C in products at the end of their shelf life, and as long shelf life (3 to 9 months) is a desired beneﬁt, the importance of maintaining the vitamin C content of juice is readily understood. Other signiﬁcant parameters like colour are also affected by oxidation (see subsection 9.2).
At the fruit processor, juice is in contact with air during extraction and ﬁnishing. Deaeration is essential in the production of NFC for bulk storage, since a high oxygen level will decrease its vitamin C level signiﬁcantly. Oxygen is less of a problem in the production of concentrate because gases are removed in the evaporator. However, if concentrate is mishandled, a large amount of dispersed air may enter the concentrate. The various steps of reconstituting orange juice from concentrate present a number of entry points for oxygen and air. Nevertheless, optimising the ﬁrst process step to avoid air entry minimises problems later in the process. Steps where particular care is needed are: handling of juice concentrate, handling of water, addition of ﬂoating cells, ﬂow in pumps and pipes, blending and reconstitution (Figure 4.4). Concentrate
Concentrate can be a source of gases. Although the solubility of oxygen in orange juice concentrate is low due to the high concentration of soluble solids, the high viscosity of concentrate makes it difﬁcult for free gas bubbles to rise to the surface. Therefore careful procedures are important during all handling steps involved with concentrate, including its transport, transfer and blending.
Pumps & pipes
Fig. 4.4 Sources of oxygen/air entry during orange juice reconstitution.
4.2 Air/oxygen in the product
Fig. 4.5 Process steps where high oxygen/air concentrations can cause problems.
Water for reconstitution is often a source of high levels of dissolved oxygen. The solubility of oxygen in cold water is about 9 mg per litre (at 20 °C). Deaeration of water before reconstitution of juice minimises dissolved oxygen. It can also eliminate the need to deaerate reconstituted juice. During certain water treatments, the carbon dioxide concentration builds up to levels that cause problems with foaming during the deaeration of juice containing ﬂoating cells.
Tank inlets should be designed to prevent air entry and foaming when the tank is ﬁlled. Juice should not be left in blending tanks for long periods before deaeration and pasteurisation, since this may lead to impaired quality due to microbial growth and vitamin C loss. Sometimes tanks are blanketed with nitrogen to prevent oxygen entry, especially in buffer tanks containing deaerated juice. 4.2.2 PROBLEMS CAUSED BY AIR/OXYGEN IN THE PRODUCT
If air gains entry during the initial reconstitution steps, it can cause problems later in the process. See Figure 4.5.
Addition of ﬂoating pulp to juice often increases its gas content. Frozen pulp contains a lot of air, both as air bubbles adsorbed to the surface of pulp particles and as free bubbles which are not released due to the high viscosity of concentrated pulp. Moreover, the agitation required to blend pulp with juice and keep the mixture homogenous in the tank increases the risks of additional gas entry. Due to gas bubbles adsorbed to cell particles, the measured oxygen content can exceed 9 ppm/litre at 20 °C.
Gas bubbles adsorbed to ﬂoating pulp reduce their density and make them ﬂoat to the top of juice. This makes it difﬁcult to maintain even distribution of ﬂoating pulp in the blending and balance tanks. Deaerator
Dissolved and dispersed gases are removed in the deaerator. Problems with foaming can occur if the incoming product contains high concentrations of undissolved gas. When juice goes from a higher pressure (in the pipes) to a lower pressure (in the deaerator), gas solubility decreases and bubbles of free gas form in the juice and build up foam. The foam formed in the deaerator and ﬁlling machine consists mainly of gas which is separated by very thin layers of liquid ﬁlm. Some foam in the deaerator does not affect its performance, but if the deaerator is ﬁlled with foam deaeration becomes insufﬁcient. This problem is mainly found with juices containing ﬂoating pulp or a lot of dispersed gas.
Pumps and pipes
Bad piping design and pumps that are not airtight can be responsible for air entry. Blending/agitation
It is important to use the right blending and reconstitution techniques. Blending in tanks should be done with low-speed agitators, and the juice should cover the agitator. In some cases, blending is carried out under a blanket of nitrogen to prevent oxygen entering the product. Using an in-line blending technique minimises oxygen ingress during reconstitution.
4.2 Air/oxygen in the product
Henry’s law states that the equilibrium concentration XA of gas A in solution is proportional to the partial pressure of gas A in the vapour phase. In order to remove dissolved oxygen (decrease XA in Henry’s law) a driving force must be applied. This can be done either by: • reducing the oxygen partial pressure (PA) above the liquid surface; • increasing the temperature (T). This will increase Henry’s constant [H(T)].
Ineffective pasteurisation can occur if juice contains very high concentrations of dispersed gas (which may lead to reduced residence time or inconsistent heating). Filling
Problems with foam in ﬁlling machines may occur for the same reasons as with deaerators, i.e. foam is formed when the pressure is suddenly released in the ﬁlling nozzle. Foaming causes decreased ﬁlling efﬁciency that can lead to: • product losses • incorrect amounts of juice in packages
A combination of these two alternatives is often used during deaeration. The partial pressure (PA) is reduced by either using a vacuum (the total pressure becomes very low) or by replacing oxygen in the gas phase with another gas. Dispersed oxygen bubbles in juice (without added ﬂoating cells) can be removed by leaving the juice in an open tank. The gas bubbles, which have a lower density than the juice, will rise to the top and gradually leave the juice with time. This process can be accelerated by creating a vacuum above the juice. However, it is still a relatively slow process. Dissolved oxygen and oxygen bubbles adsorbed to ﬂoating pulp are much more difﬁcult to remove by such a tank process. To increase the efﬁciency of deaeration, it must be made difﬁcult for the oxygen to remain in the juice, e.g. by decreasing its solubility. This can be done by: • increasing the temperature • decreasing the pressure
If the juice contains ﬂoating pulp, gas in the juice can cause poor distribution of particles in the packages (see blending tank). Storage
Oxygen takes part in many reactions that impair the quality of juice during storage. These reactions include changes in colour and taste, and degradation of vitamin C. It is therefore crucial to protect the juice against oxygen during storage. The need for protection depends on the period the juice will be stored for and at what temperature. (See Section 9.) 4.2.3 PRINCIPLES OF DEAERATION
The concentration of dissolved gases in a liquid follows physical laws. One of the more important relationships is the one deﬁned by the scientist Sir William Henry (1775–1836). A gas which is dissolved in a liquid is in equilibrium with the gas above the liquid surface. This equilibrium is given by Henry’s law.
It is important for the juice to have sufﬁcient residence time in the deaerator to allow the gas to leave the juice. By turning the juice into thin layers of liquid, the distance the gas has to diffuse from the liquid phase to the gas phase is minimised, thereby producing a high rate at which the gas leaves the juice.
concentration of gas A in the liquid phase (mole fraction). PA = partial pressure of gas A in the vapour phase (Pa). H(T) = Henry’s constant. It is a function of temperature and depends on the liquid (Pa/mole fraction).
4.3 Microbiology of orange juice
There are several types of stripping system. In one type, the liquid and the gas meet in countercurrent ﬂow as they pass through a packed column. In a another, the liquid is sprayed into a room ﬁlled with gas, or the gas is sprayed into the liquid stream before the deaerator vessel.
Methods of removing oxygen include vacuum deaeration and counter-current ﬂushing with an inert gas. Existing methods of deaeration do not remove all oxygen from juice. Nevertheless, vacuum ﬂash deaeration reduces residual oxygen to levels that no longer have a signiﬁcant impact on juice quality.
4.3 Microbiology of orange juice
In a continuous vacuum deaerator, the gases are removed from a thin ﬁlm of juice over a large area at a raised temperature and/or at a underpressure. A thin layer of juice can be achieved by: • spraying the juice through a nozzle • spreading the juice by centrifugation • distributing the juice over surface packing
4.3.1 RELEVANT MICROORGANISMS IN ORANGE JUICE
Although several microorganisms have been isolated from orange juice, few of them cause spoilage. The high acidity (low pH) of juice limits the types of microorganism that can grow in the juice. Juice spoilage is caused by microorganisms that are able to multiply in juice during its processing and storage (see Table 4.2.) The growth of microorganisms in orange juice is characterised by fermentation and/or the production of off-ﬂavours that spoil the product. Fermentation may lead to gas formation, which, in turn, results in blown packages.
When juice is sprayed through a nozzle or run over packing and/or trays, a large surface area is created for release of oxygen from the liquid to the vapour phase. Dissolved oxygen has then only a short distance to diffuse to the liquid surface. The ﬁner the nozzle or the more packing/trays, the quicker (and therefore often better) deaeration at a given temperature. However, there are practical and cost limitations. During vacuum ﬂash deaeration, usually about 1 % of the liquid is vaporised. As the vapour contains some volatile ﬂavour components, it has to be condensed back into the juice. This can be done either by an internal or an external condenser that chills the vapour back to a liquid state. In both cases, the temperature of the cooling water in the condenser and the vacuum applied will determine the amount of ﬂavour components condensed.
TABLE 4.2 THE PREDOMINANT MICROORGANISMS IN ORANGE JUICE Acid-tolerant bacteria Yeasts Moulds
Lactic acid bacteria belonging to the genera Lactobacillus and Leuconostoc are the most common acid-tolerant bacteria that cause spoilage of orange juice (see Figure 4.6). Spoilage is characterised by a “buttery” or “buttermilk-like” ﬂavour resulting from the formation of diacetyl during bacterial growth. Leuconostoc and many species of Lactobacillus also produce large amounts of CO2.
In the gas-stripping type of deaerator, the partial pressure of oxygen in the vapour phase is reduced to almost zero by displacing the oxygen with another gas, e.g. nitrogen (N2) or carbon dioxide (CO2). By removing the oxygen in the vapour phase above the liquid, the oxygen in the juice is forced out from the juice into the vapour phase. This process does not reduce the total gas content of the juice but replaces oxygen with another gas.
4.3 Microbiology of orange juice
The optimal growth temperature for most yeasts is 20–30 °C. They are more tolerant of cold temperatures, high osmotic pressure and lack of nutrients than bacteria or moulds. Species of yeasts can easily survive in citrus concentrates of 58 to 65 °Brix and in frozen juices.
are the most common “Yeasts type of spoilage organism ” Saccharomyces cerevisiae, Rhodotorula spp and Zygosaccharomyces spp are the most common yeasts present in juice. Saccharomyces cerevisiae is most commonly associated with the spoilage of pasteurised citrus juices. The presence of Rhodotorula may be indicative of poor postpasteurisation hygiene. Zygosaccharomyces is an osmophilic yeast, which means that it can survive the high osmotic pressures and low water activity of concentrated orange juice. It is frequently associated with spoilage of concentrates.
Fig. 4.6 Different shapes of lactic acid bacteria.
Most lactic acid bacteria grow best in orange juice at temperatures between 20 and 37 °C. Their rate of growth is greatly reduced above or below these temperatures. Growth is very slow at 4 °C in single-strength juice. These bacteria are sensitive to heat and high osmotic pressure (high juice concentration); no growth is observed in juice above 45 °Brix. Lactic acid bacteria pose the biggest problem during the processing steps prior to concentration. After extraction, the juice has to be refrigerated or heat-treated as soon as possible to prevent the build-up of large populations of these bacteria. It is also important for fruit processors to maintain an effective programme of sanitation. The main species of lactic acid bacteria causing spoilage are Lactobacillus plantarum, Lactobacillus brevis, Leuconostoc mesenteroides and Leuconostoc dextranicum. Yeasts
Fig. 4.7 Yeasts showing budding reproduction.
Yeasts (see Figure 4.7) are the most common type of spoilage organism in both single-strength and concentrated orange juice. Spoilage of orange juice by yeasts typically results from an alcoholic fermentation which leads to off-ﬂavours and CO2 production. Yeasts not capable of alcoholic fermentation may cause turbidity, ﬂocculation and clumping in juice.
4.3 Microbiology of orange juice
Some moulds that have been isolated from orange juice are: Aureobasidium pullulans, Aspergillus niger, Botrytis spp, Fusarium spp, Geotrichum spp, Mucor spp, Aspergillus fumigatus, Cladosporium spp and Penicillium spp.
Fig. 4.8 Example of mould structure.
The presence of pathogenic microorganisms in orange juice is rare. The low pH of juice inhibits growth of pathogens, but long-term survival of some pathogens in refrigerated orange juice is possible. Outbreaks of disease, particularly salmonellosis, traced back to orange juice have occurred as a result of consuming unpasteurised orange juice, or due to reconstituted juice becoming contaminated before serving. Diseases attributed to orange juice are mainly caused by incorrect product handling and can be prevented by carrying out approved sanitary procedures, pasteurising the juice, and by preventing product contamination after pasteurisation.
Moulds form colonies of aerial mycelia on the surface of juice, and ﬂocculation or ﬂoating mycelia within juice (see Figure 4.8). They can grow under a wide variety of conditions. In general, moulds grow well in acid media and require abundant oxygen. Moulds that grow in orange juice are generally sensitive to heat treatment and are thus easily destroyed by pasteurisation. Compared with yeasts and bacteria, moulds have only infrequently been associated with spoilage of orange juice. This is because of their aerobic (oxygen-dependent) nature and slow growth rates. However, with the advent of longterm chilled storage of single-strength juice and extended shelf life of juice in nonaseptic cartons with oxygen barriers, mould growth in citrus juice has become a more important issue. Moulds may give rise to concern during juice extraction when fruit-handling and juice room equipment is not kept in hygienic condition. When the correct approach to sanitation is neglected, moulds colonise the surfaces of conveyor belts, fruit bins, extractors and other equipment. These conditions promote the contamination of juice or the surfaces of containers.
Most bacterial spores cannot grow in fruit juices with a pH below 4.5. Though very rare, thermoresistant acidophilic bacteria have been isolated from shelf-stable juices. In 1992 these strains were classiﬁed in a new genus called Alicyclobacillus. Microorganisms belonging to this genus have a preference for thermophilic temperatures with an optimum temperature around 45 °C, and they will most likely not grow below 20 °C. The most likely source of contamination of fruit juices is fruit contaminated with soil during harvesting. Such contamination is introduced into the manufacturing process through unwashed or poorly washed fruit. A spoilage characteristic of this type of bacteria has been described as an off-ﬂavour like “disinfectant” or guaiacol. No gas production has been observed.
4.3 Microbiology of orange juice
Not-from-concentrate juice, NFC
4.3.2 MICROFLORA OF DIFFERENT TYPES OF ORANGE JUICE
After pasteurisation, NFC is either ﬁlled directly into consumer packages or, more often, stored in bulk for a period of time under chilled aseptic or frozen conditions. Generally, microbial spoilage of pasteurised single-strength juice sold chilled under nonaseptic conditions is due to fermentative yeasts. The most common spoilage organism in this product is Saccharomyces cerevisiae, although other yeasts have occasionally been isolated as well. The microﬂora of NFC strongly depends on juice storage temperature. At temperatures ≤7 °C yeasts are the predominant ﬂora responsible for spoilage, whereas at ≥10 °C lactic acid bacteria outgrow the yeasts and become the main spoilage organisms. The main species present are lactic acid bacteria, such as Lactobacillus spp, Leuconostoc spp, and yeasts like Zygosaccharomyces spp and Saccharomyces cerevisiae.
The microﬂora of different orange juice products can vary widely according to the state of raw fruit, and juice processing and storage conditions. Frozen concentrated orange juice
FCOJ is not aseptic or commercially sterile. It can contain abundant microﬂora of wide diversity including yeasts, moulds and bacteria. However, frozen orange juice concentrate does not have any signiﬁcant microbial problems because it is stored frozen. Concentrated orange juice quite often has a total microbial population around 100 to 1,000 organisms/ml. In general, an acceptable microbial quality of concentrate is a total viable count lower than 1,000/ml; for yeasts in the range of 100/ml, and for moulds lower than 10/ml. When concentrate is exposed to temperatures above freezing point, osmophilic yeasts like Zygosaccharomyces spp are the primary spoilage organisms.
Freshly squeezed orange juice – unpasteurised
The total number of microorganisms in this product varies throughout the season and is strongly dependent on the condition of the fruit and sanitation of the processing equipment. In general, higher counts are observed with mature oranges that have a higher ratio (Brix:acid). Much higher counts are observed with unsound fruit. The hygienic condition of the processing plant will also inﬂuence the number of microorganisms present in juice. In general, freshly squeezed orange juice has a total microbial count ranging from 1,000 to 10,000 organisms/ml. However, this number may be as high as 32,000,000 organisms/ ml in juice extracted from poor-quality oranges in processing plants with bad sanitation.
Reconstituted orange juice from concentrate
As yeasts represent the dominant microﬂora of any consequence in concentrate, it is most likely that they will remain so in juice reconstituted from concentrate. Nevertheless, if reconstitution is not carried out under appropriate sanitary conditions, the type and number of microorganisms in the end product will increase. Microorganisms normally present in the sur rounding air and water, and on equipment, can contaminate juice. Juice should not be held in tanks for long periods of time before pasteurisation. Whenever concentrate is reconstituted to single-strength juice, microorganisms that were dormant in the concentrate are suddenly provided with the conditions that allow them to grow rapidly. After dilution of concentrate but prior to pasteurisation, juice is held in tanks. These require proper cleaning procedures to prevent them from becoming a source of contamination.
4.3 Microbiology of orange juice
Juice not from concentrate
Chilled/ frozen storage
Juice from concentrate
Reconstitution Frozen storage
Fig. 4.9 Orange juice pasteurisation steps.
The low pH of juice and a rapid juice reconstitution process usually sufﬁce to prevent the build-up of large microbial populations in juice. Furthermore, as reconstituted juice is pasteurised before packaging, microorganisms of concern will be destroyed. However, if a plant has poor cleaning routines and reconstituted juice is held in tanks for a long time prior to pasteurisation, high populations of microorganisms can become established. This will demand higher pasteurisation temperatures to completely destroy the microorganisms. In fruit processing plants, microbial contamination is controlled by three different levels of cleaning: • Frequent cleaning during everyday production which is necessary to maintain the hygienic appearance of equipment. • Intermittent-type cleaning while plant is in operation, or cleaning parts of the plant temporarily taken out of production in order to clean them properly. • General cleanup of the plant which occurs when the plant is completely shut down.
4.3.3 INFLUENCE OF RAW MATERIALS Fresh fruit
Microorganisms found in nature will enter the processing plant via fruit, soil, animals and people. Their number will vary depending on harvesting method as well as handling on the way from the groves to the processing plant. Out of the large variety of microorganisms, only those species capable of growing during the production of orange juice are of prime concern. These are lactic acid bacteria, yeasts and moulds. Fruit grading and washing
There is a correlation between the percentage of defective fruit entering a processing plant and the contamination of extracted juice. To minimise microbial contamination within a plant, fruit must be carefully graded and washed effectively. In some cases fruit is treated with detergent to minimise surface microorganisms. All unsound fruit should be removed. Washing is usually done with (chlorinated) water sprays located at strategic points on conveyor belts and elevators. The sprays must cover the entire width of the belt completely, otherwise microorganisms will accumulate at the edges of the belt. Washing efﬁciency has a direct bearing on the microbial population of extracted juice.
Flushing with chlorinated water is generally performed periodically to control microbial contamination while the plant is in operation. Floors should not be cleaned during operation of the production line because this can spread microorganisms. Cleaning-in-place (CIP) systems that greatly improve the efﬁciency of cleaning are now generally used by processing and packaging plants. See also subsection 7.9.
Effective cleaning procedures are essential in controlling microbial contamination in production of orange juice concentrate, as well as during reconstitution of concentrate to produce singlestrength orange juice.
4.4.2 INACTIVATION OF ENZYMES
Cloud loss of single-strength juice and gelation in concentrate are mainly caused by pectin methyl esterase, which is present naturally in fruit. PME is mainly active in the temperature range from 5 to 65 °C and shows maximum activity at 60 °C. Above 60 °C its activity gradually decreases. The activity of the enzyme at temperatures below 5 °C is low, but it is still enough to cause cloud loss in single-strength orange juice. Even at a temperature as low as –18 °C the reaction rate is high enough to cause gelation of concentrates during storage.
4.4.1 PURPOSE OF PASTEURISATION
The purpose of pasteurisation is to make the juice product stable during subsequent processing and storage. Pasteurisation of orange juice is necessary for destroying the microorganisms capable of growing during storage, and for inactivating enzymes to prevent cloud loss. Enzymes are proteins that catalyse biological reactions. They are necessary for the growth of all living matter. Orange juice is pasteurised at least twice before it reaches the consumer (except for a small amount of NFC that is ﬁlled directly into consumer packages). The ﬁrst pasteurisation occurs immediately after extraction prior to bulk storage, and the second pasteurisation occurs before packaging (see Figure 4.9). The ﬁrst pasteurisation is necessary to completely inactivate the enzyme pectin methyl esterase (PME), also known as pectin esterase (PE), which will otherwise cause cloud loss of single-strength juice and gelation of concentrate during storage. Microorganisms of commercial interest are also killed by this process. The second pasteurisation destroys any microorganisms that may have contaminated juice after the ﬁrst pasteurisation step and survived bulk storage, as well as those which may have contaminated juice during its reconstitution from concentrate.
A given enzyme will only split cer tain molecules, and only at certain bonds.
FACTS ABOUT ENZYMES Enzymes are proteins produced by living organisms specialised in catalysing biological reactions. They are therefore sometimes called biocatalysts. Enzyme action is speciﬁc; each type of enzyme catalyses only one type of reaction. The action of an enzyme is also strongly inﬂuenced by temperature and pH. The basic function of an enzyme that breaks down a larger molecule into smaller ones is illustrated in Figure 4.10. The enzymes in orange juice come from the fruit itself. They are ﬁrmly associated with the cell wall fractions and therefore are mainly derived from parts of orange like peel, rag and juice sac tissue (pulp). Enzymes are released from the fruit solid phase (membranes) into the liquid phase (juice) during the extraction process.
The enzyme ﬁts into a particular spot in the molecule chain, where it weakens the bond.
Fig. 4.10 The basic function of an enzyme.
The molecule splits. The enzyme is now free to attack and split another molecule in the same way.
• Among orange varieties from Brazil (Pera Rio, Pera Coroa, Natal and Valencia), PME in Valencia and Pera Rio juice had the highest heat resistance, requiring 2 min at 90 °C for complete inactivation, whereas PME in Pera Coroa and Natal varieties was inactivated after 1.5 min at 90 °C. • Juice with higher pH requires a more intensive heat treatment to inactivate PME than juice with lower pH. The inﬂuence of pH on thermal inactivation of PME is dependent on fruit variety. Orange juice from the Pineapple variety showed the highest sensitivity to pH changes, followed by Valencia. • As PME is associated with cell wall materials, a higher heat load is required in juices with higher pulp content. An increase of pulp content from 5 to 10 % increases by about 2.5 times the time required at a given temperature to inactivate PME.
D value (sec)
Fig. 4.11 Decimal reduction time (D value) for PME in Valencia orange juice at pH = 4.1 and with 12 % pulp content.
The most common reason for cloud loss or gelation in orange juice is the enzymatic breakdown of pectin molecules in the juice. Pectin is a complex organic substance (consisting mainly of partially methylated sugar units) that exhibit important properties, such as the ability to form emulsions and to increase liquid viscosity. In single-strength orange juice, pectin is one important constituent of the cloud. The cloud of orange juice contributes to its visual appearance (opacity) and viscosity. Viscosity is essential for good juice “mouthfeel”. The enzyme breaks down pectin by removing methyl groups from the sugar units. The resulting molecule reacts with calcium (naturally present in the juice) to create bridges between the sugar units, see Figure 4.12. The insoluble molecule formed is called calcium pectate. In single-strength juice, calcium pectate settles to the bottom of the package. This causes separation of the juice into a clear upper phase and a lower sediment phase. This separation is referred to as cloud loss. In orange juice concentrate, calcium pectate forms gel-like lumps due to the high sugar and acid content. This gelation makes it impossible to reconstitute to orange juice of good quality.
In order to prevent cloud loss or gelation during processing and storage of orange juice, it is necessary to inactivate PME. Although several methods have been tested, pasteurisation is the only process used industrially to inactivate the enzyme. The time-temperature conditions to inactivate PME are dependent on : • juice pH • juice pulp content • fruit variety/maturity From the literature it is known that: • Among the varieties of oranges from Florida (Valencia, Pineapple and Hamlin), the heat stability of PME was highest in juice from Valencia oranges, and similar in juice from Pineapple and Hamlin oranges. Figure 4.11 shows the decimal reduction time for PME in Valencia oranges grown in Florida. The D value correspond to 90 % enzyme inactivation. A heat load corresponding to 2–3 D values is generally sufﬁcient for inactivation of the enzyme.
The second pasteurisation, carried out prior to juice packaging, involves NFC after bulk storage or juice reconstituted from concentrate. It is for microbial destruction rather than inactivation of enzymes. Since microorganisms are less heat resistant than enzymes, the second pasteurisation may be carried out at a lower temperature than the ﬁrst pasteurisation. The required time-temperature combination for the second pasteurisation will depend on the total number of microorganisms in the juice to the pasteuriser. This population of microorganisms depends on the initial number in the concentrate, residence time in tanks before pasteurisation and the standard of plant sanitation.
O O-CH3 C
Pectin methyl esterase Cacium (Ca2+) Pectin bridges methylesterase -
O O CH3OH C
Fig. 4.12 The action of the enzyme pectin methyl esterase (PME).
4.4.3 INACTIVATION OF MICROORGANISMS
The heat-resistance of microorganisms is affected by factors like pH, water activity and oxygen. The reduction of microorganisms is more efﬁcient under conditions not favourable for their growth. In general, moulds are less resistant to heat than yeasts and yeasts less resistant to heat than bacteria. The yeast Saccharomyces cerevisiae is the most common spoilage organism in citrus juices. It can form ascospores that are much more heat-resistant than its vegetative cells.
FACTS ABOUT THERMAL PROCESSING The use of heat for a given period of time is a method of food preservation used to destroy microorganisms, enzymes and heat-labile toxins. Pasteurisation and sterilisation are two types of thermal processing. Sterilisation destroys all living microorganisms including microbial spores, whereas pasteurisation kills the majority of vegetative microorganisms, particularly pathogenic bacteria, but has little or no effect on bacterial spores. Pasteurisation is generally adequate heat treatment for highacid juice foods.
4.4.4 TIME-TEMPERATURE CONDITIONS FOR PASTEURISATION
Thermal resistance of microorganisms is tradi tionally expressed in terms of D values and z values. These are deﬁned as follows:
In orange juice, PME is more heat-resistant than the microorganisms commonly present in orange juice. This means that a more intensive time-temperature treatment is necessary to inactivate the enzyme than to destroy microorganisms.
D value: D value, or decimal reduction time, is the time required at a given temperature to decrease the population of a speciﬁed microorganism by 90 % or one log cycle. For example, D80 = 1 min means that it takes 1 minute at 80 °C to destroy 90 % (or one logarithmic reduction) of the speciﬁed microorganism.
Orange juice should be pasteurised to inactivate PME as soon as possible after extraction. It is pasteurised above 95–98 °C for 10–30 sec. This can be done as a separate step or as a ﬁrst step in the evaporator.
z value: This is the change in temperature needed to alter the D value by one log cycle. For example, if an organism has a z = 5 °C and a D80 °C = 1 min, the D85 °C = 0.1 min and the D75 °C = 10 min.
Pectin methyl esterase
Ascospores Time (sec)
Fig. 4.13 Theoretical thermal destruction curves of pectin methyl esterase, ascospores and vegetative cells of Saccharomyces cerevisae in orange juice.
Figure 4.13 shows the theoretical thermal destruction curves of pectin methyl esterase, and of ascospores and vegetative cells of Sac. cerevisae in orange juice. All temperature/time combinations to the right of the ascospore curve are sufﬁcient for 10 decimal reductions or more. The blue square shows the time/temperature combinations used mainly by the industry today. Since microorganisms grow much slower at chilled than at ambient temperatures, chilled juice can be sold as a nonaseptic product, i.e. nonaseptic ﬁlling and packaging can be used. However, the pasteurisation step must ensure that microorganisms in the juice will not spoil it during its intended shelf life.
intensive time-temperature “More treatment is necessary to inactivate
Temperatures from 80 °C up to 95 °C for 15–30 sec. are commonly used by the industry for the second pasteurisation of orange juice reconstituted from concentrate and intended for storage at ambient temperature. However, the industry is now showing an increasing interest in lowering the pasteurisation temperature and/or holding time. As already mentioned, Saccharomyces cerevisiae is the most common spoilage agent in orange juice. This species of yeast produces ascospores, a more resistant form of yeast cell. Based on the heat-resistance of this microorganism, (D60 = 3–19 min), a heat treatment of 75–80 °C for 15–20 seconds will be adequate to sufﬁciently reduce the microbial population (second pasteurisation) provided that the raw material is of good quality. When aseptically packed, this product can be stored under ambient conditions.
the enzyme PME than to destroy microorganisms
In section 5 you will read about: • The production steps in a processing plant. • Fruit delivery and what is done at the fruit reception area to prepare oranges for juice extraction. • How the maximum amount of juice is squeezed from fruit and the two principal extractor types. • Removing pulp by clariﬁcation so that juice can be evaporated to concentrate or processed to single-strength juice.
• NFC production including heat treatment and bulk storage. • Concentrate production and the need for efﬁcient evaporators. • The recovery of peel oil. How winterisation makes wax drop out. • The production of animal feed from waste streams. • Pulp production and the many uses of pulp. • Washing of pulp to recover valuable solids.
5. Fruit processing
Frozen storage tanks
Refrigerated aseptic storage
Frozen drum storage Defect removal
Wet peel, rag, seeds
Frozen drum storage
Fig 5.1 Flow chart showing typical processing steps found in an orange processing plant.
A box of oranges is deﬁned as containing 40.8 kg (90 lb) of fruit. In Florida, the small/ medium-size plants typically process 5–10 million boxes (200–400,000 tonnes) per season, the large plants up to 25 million boxes. Most Brazilian citrus plants have much higher capacity. The world’s largest orange juice plant, Citrosuco at Matao, Brazil, can take in 60 million boxes (2.4 million tonnes) of fruit during a season. In most other orange-growing regions, citrus processing plants are considerably smaller than those in Florida and Brazil. Typical orange processing steps are shown in Figure 5.1.
5.1 Processing plant overview Orange processing plants are located in the vicinity of the fruit growing area. Fruit should be processed as soon as possible after harvesting because fruit deteriorates quickly at the high temperatures found in citrus-growing areas. Orange products, on the other hand, are produced in a form that allows them to be stored for extended periods and shipped over long distances. In the orange industry, the basic unit of reporting crop and plant intake is commonly the fruit box.
5.1 Processing plant overview
Not-from-concentrate juice (NFC) production
Fruit is delivered in trucks which discharge their loads at the fruit reception area. The fruit may be prewashed to get rid of immediate surface dirt and pesticide residue before any leaves and stems still attached to the fruit are removed. Then follows pregrading by manual inspection to remove any unsuitable fruit. Sound fruit is conveyed to storage bins. Damaged fruit goes directly to the feed mill.
Instead of concentrate production, juice may be processed at single strength as an NFC product. Clariﬁed juice is pasteurised before storage. Deoiling may be required to reduce oil levels in the juice, and deaeration to remove oxygen is part of good practice. Since the product is consumed year-round but production is seasonal, NFC may be stored for up to one year. It is stored in bulk either frozen or under aseptic conditions.
Extraction involves squeezing or reaming juice out of either whole or halved oranges by means of mechanical pressure. After ﬁnal washing and inspection, the fruit is separated according to size into different streams or lanes. Individual oranges are directed to the most suitable extractor in order to achieve optimum juice yield. As the extraction operation determines juice yield and quality, the correct setting of extractor operating conditions is very important.
For pulp recovery, pulpy juice from the extractor is passed through a system that removes defects where undesirable pulp components, such as seed and rag, are removed. The clean pulp stream is then concentrated in a primary ﬁnisher. After heat treatment, the pulp slurry is typically concentrated further before being sent to frozen storage. Pulp wash
If the pulp fraction is not recovered for commercial sale, pulp from the ﬁnal juice ﬁnishers and clariﬁers can be washed with water to recover juice solubles. This stream is called pulp wash and may, legislation permitting, be blended with juice before concentration.
After extraction, the pulpy juice (about 50 % of the fruit) is clariﬁed by primary ﬁnishers which separate juice from pulp. The ﬁnishing process is a mechanical separation method based on sieving. The juice stream is further clariﬁed by centrifugation. The pulp stream, containing pieces of ruptured juice sacs and segment walls, may then go to pulp recovery or to pulp washing.
Peel oil recovery
Recovered peel oil represents some 0.3 % of the fruit intake. The emulsion of oil and water coming from the extractor section is clariﬁed by centrifugation in two steps. The puriﬁed oil contains dissolved waxes which are removed by winterisation (refrigeration) of the oil for a certain time.
Frozen concentrated orange juice (FCOJ) production
From the buffer/blending tanks and after clariﬁcation, juice goes to the evaporator. Within the evaporator circuit, the juice is ﬁrst pre-heated and held at pasteurisation temperature. It then passes through the evaporation stages of the process where it is concentrated up to 66 °Brix. During the evaporation process, volatile ﬂavour components ﬂash off and can be recovered in an essence recovery unit. Juice concentrate is cooled and blended with other production batches as required to level out ﬂuctuations in quality. It then goes to frozen storage in tanks or drums as FCOJ, sometimes for several years.
It is economically feasible to include a feed mill operation in larger processing plants. Rejected fruit from grading, peel and rag from extraction, and washed pulp and other solid waste are sent to the feed mill where it is dried and pelletised for animal feed. Smaller plants usually truck their solid waste to a plant with a feed mill or dispose of it in other ways, such as landﬁll.
5.2 Orange juice production steps
5.2 Orange juice production steps
Picking of fruit
All production steps for orange juice, from orange fruit to packaged product, are shown in the block diagram Figure 5.2. The steps carried out in the fruit processing plant as highlighted in the ﬁgure are discussed in more detail.
Peel oil recovery Peel, rag, seed
Feed mill Pulpy juice
Pulp wash production
Not from concentrate juice production
Concentrate pr production
Fig. 5.2 Production steps for orange juice. Bulk transport
5.3 Fruit reception
Final fruit wash
Fig. 5.3 Processing ﬂow for fruit reception. Fruit storage
5.3 Fruit reception
The pregraded fruit is stored in bins specially designed with inclined multilevel internal bafﬂes. These distribute the fruit evenly in the bin to prevent too much weight pressing on fruit. The procedure of holding the fruit in storage bins in order to reduce juice acidity and increase the ﬁnal juice ratio needs to be applied with care, because passing fruit through bins usually reduces the ﬁnal juice yield compared with direct processing. Besides the main function of storing fruit with different characteristics to provide processing options and the desired juice quality, correct management of stored fruit also make it possible to avoid very wide ﬂuctuations in the Brix: acid ratio of raw juice. Such ﬂuctuations are usually the main cause of hesperidin-related defects formed during evaporator operation and found in the ﬁnal juice concentrate. A good procedure is to minimise the time fruit stays in storage bins, preferably less than 24 hours. Storage for longer times, however, does occur.
After harvesting, fruit picked in the groves is loaded onto trucks (typically 20 tonnes in Florida) and taken to the processing plant. Figure 5.3 shows the subsequent processing ﬂow at the fruit reception. Truck unloading
The trucks are unloaded onto a specially designed tipping ramp. The ramp lifts the front of the truck to allow the fruit to roll off the rear of the trailer directly onto a conveyor. The fruit is then conveyed to the prewash station. Alternatively, the truck may be reversed down a ramp so that the fruit is unloaded directly onto a conveyor. Prewashing, destemming and pregrading
The fruit may undergo initial washing to remove dust, dirt and pesticide residues. Some processors have discontinued washing the fruit before bin storage because wet fruit in the bins can make downstream sanitation more difﬁcult. The fruit then moves on to destemming and pregrading. The roller conveyor of the destemming and pregrading tables allows any leaves or twigs to fall through the conveyor bed. Pregrading by manual inspection removes rotten and visibly damaged fruit. Rejected fruit, known as culls, may be sent to the feed mill. Water used for prewashing is often condensate recovered from the evaporation process. There is a strong desire to reduce total water consumption in orange processing plants.
Fruit is drawn from the storage bins into the surge bin where fruit from one or more storage bins may be combined. Final fruit washing
Thorough washing of the fruit is carried out immediately before the extraction process. The wash water may include a mild disinfectant to help reduce the microbial population on the fruit surface. Fresh water or condensate recovered from the evaporators is used for ﬁnal washing.
A sample of fruit is taken for analysis from each truck. The main parameters analysed are juice yield, °Brix, acidity and colour. This gives the processor an indication of fruit ripeness. As the fruit goes into bin storage, each load can be tagged and identiﬁed. It is then possible to select suitable fruit from various sources for blending during the extraction process to achieve the desired ﬁnal product quality. The measured juice yield may also form the basis for payment to the fruit supplier.
The fruit passes over a series of grading tables for ﬁnal visual inspection where damaged or unsuitable fruit is removed.
5.4 Juice extraction
Peel oil extraction
Pulpy juice Oil emulsion
Wet peel, rag, seeds
Fig. 5.4 The juice extraction process.
Peel oil recovery
Wet peel, rag, seeds
5.4 Juice extraction
The aim of the juice extraction process (see Figure 5.4) is to obtain as much juice out of the fruit as possible while preventing rag, oil and other components of the fruit from entering the juice. These may lead to bitterness in taste or other defects later during juice storage. The extraction operation determines product quality and yield, and therefore has a major effect on the total economics of the fruit processing operation. Once the fruit has been washed and graded (inspected), it is ready for the extraction process. To optimise extractor performance, the raw fruit must be sorted according to size because individual extractors are set to handle fruit of only a certain size range.
After grading, the fruit passes over the sizing table which divides the fruit into different streams according to fruit diameter. A sizing table is generally made up of a series of rotating rollers over which the fruit passes. The distance between the rollers is preset, and increases as the fruit travels over the table. Over the ﬁrst set of rollers, the smallest fruit drop between the gap onto a conveyor which carries them to an extractor set for their particular size range. As the gap increases, larger fruit will pass through the rollers onto extractors set for their deﬁned size range. In this way, all the fruit is selected to suit the individual settings of the extractors. There are normally 2–3 different size settings in an extractor line. A well-functioning fruit sizer is essential to producing juice of high quality and/or yield. If the fruit is too big or small, then (depending on the extractor type) it will be oversqueezed and excessive rag and peel will get into the juice with resulting bitterness. If the fruit is undersqueezed, insufﬁcient yield will result.
THREE STREAMS RESULT FROM THE EX TRACTION SECTION
5.4.1 EXTRACTOR TYPES Oil emulsion, containing oil from the peel and water, goes to peel oil recovery.
Two types of extractor dominate in orange processing plants, the squeezer type and the reamer type. For these two types there are two major brands, FMC (squeezer type) and Brown (reamer type). Both extraction systems are dedicated to citrus fruit. The reamer-type extraction system provides excellent separation of the orange components juice, oil and peel.
Wet peel together with pulp, rag and seeds, ﬂows directly to the feed mill. Pulpy juice, goes to clariﬁcation and then production of concentrate or NFC. Pulp intended for sale as pulp goes to pulp production. Residual pulp goes to pulp washing or the feed mill.
5.4 Juice extraction
It works best – as regards both product quality and yield – with fruit round in shape and of uniform ripeness such as found with Florida fruit. Squeezer-type extracFig. 5.5 A squeezer-type orange juice extractor. tors are less sensitive to the size and shape of the fruit but can lead to higher oil content in the juice and more damaged pulp compared with reamer-type extractors. Adjustments to the standard squeezer-type extractor may be needed to keep oil levels low and/or improve pulp quality. Globally, squeezer-type extractors are the most common. However, in Florida, the total installed extraction capacity is about equal for both types of extractor. The major share of the NFC produced in Florida is extracted using reamer-type extractors. Another type of extraction equipment is the rotary press extractor. These are more multipurpose machines and therefore may also be used to process other types of fruit. With rotary press extractors, the fruit is cut in half and the halves pass between rotating cylinders which press out the juice. Oil is extracted from the peel in a separate step prior to extraction. Although the extraction process is simple, both juice yield and quality are less optimal compared with squeezer-type and reamer-type extractors. Rotary press extractors, which have a high capacity per unit and require lower investment, are popular in the Mediterranean area. However, globally they are of minor importance compared with squeezer- and reamer-type extractors. Once installed in a plant, extraction systems are not easily interchangeable due to the different demands on the surrounding equipment.
5.4.2 THE SQUEEZER-TYPE EXTRACTOR
A squeezer-type extractor is shown in Figure 5.5. These are placed in lines in the extractor room with up to 15 extractors per line. Each extractor may be ﬁtted with 5 heads, which are available in different sizes so that they can handle the type and quality of fruit available. Typical sizes are 23⁄8, 3, 4 and even 5 inches (used mainly for grapefruit). The head size for each extractor in a line is chosen to optimise the handling of sized fruit. The extractor separates the fruit into four parts – pulpy juice, peel, core (rag, seeds and pulp) and oil emulsion. Fig. 5.6 Operation of the squeezer-type orange juice extractor. Water Whole fruit
Juice manifold Oil emulsion
Pulpy juice Core
The head of an extractor comprises an upper and a lower cup (see Figure 5.6). The cups have metal ﬁngers that mesh together as the upper cup is lowered onto the lower cup. A cutter comes up through the centre of the lower cup to cut a hole through the skin in order to allow the inner parts of the orange to ﬂow out. The cutter is part of the perforated strainer tube, sometimes referred to as the preﬁnisher. Once the strainer tube has cut into the fruit, the upper cup squeezes down on the lower cup. This pressure initially forces the juice to burst out of the juice vesicles and pass through the perforations of the strainer tube. Some of the pieces of the ruptured juice sacs (i.e. pulp) will pass through with the juice. The upper cup continues to squeeze down on the lower cup to extract as much juice as possible.
are two major types “There of extractor system, squeezer type and reamer type
5.4 Juice extraction
Eventually, the downward pressure causes the peel to break up, disintegrate and pass up through the ﬁngers of each cup. Juice ﬂows through the strainer tube into the juice manifold. The core material is discharged from the bottom of the strainer tube through the oriﬁce tube. As the peel is forced through the ﬁngers of the cups during the last step of the extraction cycle, oil is released from the peel. The bits of peel are washed with recycled water to extract the oil from the oil sacs. The oil is discharged from the extractors as an emulsion with water. With squeezer-type extractors, one item of equipment – the extractor – separates the fruit into four principal product streams in one basic step. It is claimed that contact is avoided between the juice and oil, and the juice and peel. For successful operation of this equipment, the correct selection of cup size and adjustment of cup and cutter operation are important. Too much pressure applied to fruit resulting from the use of undersize cups may result in blowing out the fruit and/or peel entering the juice stream. If too little pressure is applied the yield will drop. The throughput of a ﬁve-head extractor will vary according to the quality and size of fruit. The standard operating speed is 100 rpm, or 500 oranges per minute. Fruit will not always ﬂow to each cup; 90 % utilisation is a high ﬁgure. A typical capacity for medium-sized fruit is 5 tonnes/hr of fruit per extractor, corresponding to about 2500 l/h of juice. Because extractors operate at a ﬁxed number of oranges processed per minute, the citrus processing plant throughput is very sensitive and dependent on fruit size. Processing small fruit (350 oranges/box) will result in 1500 l/h juice ﬂow rate instead of 3000 l/h when processing large fruit (180 oranges/box), an increase of 100 % related to the quantity of juice and by-products handled by downstream equipment. These ﬁgures show the importance of correct storage bin management and fruit size in smooth factory operations.
Modiﬁcations for premium pulp
As the pulpy juice passes through the holes in the strainer tube in the standard extractor, the pulp tends to be broken up into small pieces, typically 2–3 mm in length or less. This is acceptable if the pulp is intended for pulp wash and as commercial pulp for certain markets. Market demands in the juice market are changing, and the need for more “natural” pulp that has been subjected to less shear is increasing. In a squeezer-type extractor of modiﬁed design, larger pulp pieces, up to 15–20 mm long, ﬂow along with the juice stream. The main difference in design is the use of a modiﬁed strainer tube with larger openings that allow more pulp to remain in the juice stream. The pulp is subsequently separated from the juice and treated in a modiﬁed pulp recovery system. Modiﬁcations to the squeezer-type extractor to suit premium pulp were introduced in the 1990's and today there are several installations in Florida and Brazil. Premium juice “low-oil” extractor
Certain fruit varieties (e.g. the Florida Valencia) will express more oil into the juice stream than other varieties. This can lead to oil content in the juice exceeding acceptable levels (such as 0.035 %, the maximum level permitted in Florida for grade “A” juice). This is a problem with NFC but less so with juice intended for concentrate because most of the oil will ﬂash off in the evaporator. In the lowoil version of the squeezer-type extractor, the design of the strainer tube and oriﬁce tube area are modiﬁed. This unit cuts a smaller core and puts less pressure on the fruit during extraction, thereby reducing the amount of peel oil getting into the juice. These modiﬁcations may also lead to a reduction in juice yield. When the top spray of water is stopped, the amount of peel oil to be recovered is thereby reduced. As an alternative, hermetic centrifuges or vacuum ﬂashing can be used for deoiling the singlestrength juice in conjunction with the standard extractors. This allows a higher juice yield to be maintained during extraction, while excess oil is removed after the extraction process.
5.4 Juice extraction
5.4.3 THE REAMER-TYPE EXTRACTOR
The reamer-type extractor is based on the same principle as a typical manual kitchen squeezer used to prepare orange juice for breakfast. An extraction line comprises several extractors, and it is very important to set up each extractor to suit the size of fruit fed into it. A reamer-type extractor is illustrated in Figure 5.7. Fruit is fed into the feed wheel and cut in half. The halves are oriented and picked up in synthetic rubber cups mounted on a continuous belt system. A series of nylon reamers (cone-shaped inserts that have ridges moulded into the form from tip to base of the reamer) are mounted on a rotating turntable. The reamers, in the vertical plane for most models, enter each fruit half and rotate as they penetrate them. The speed of rotation varies as the reamer penetrates the fruit, being slower towards the end of the operation. Juice, pulp, rag and seeds pass out through one outlet, and the remaining peel passes out through the peel chute. The juice and pulp are separated from the rag and seeds by a strainer, then pass on to the ﬁnishers. The size, pressure and rotation speed of the reamer can be adjusted to suit the maturity, size and quality of fruit. The reamer-type system typically gives a better quality of pulp (longer and larger cell fragments) than standard squeezer-type extractors. Juice yields between the two systems are comparable.
Fig. 5.7 A reamer-type orange juice extractor. The oil extraction system
Peel oil can be recovered from the peel using a separate oil extraction system which is placed upstream of the juice extractors. It operates on the principle of puncturing oil sacs in the ﬂavedo and washing the oil out to make an emulsion (see Figure 5.8). In the ﬁrst stage of the oil extraction system, whole fruit passes over a series of rollers with small but sharp needle-like projections. The oil glands are pricked rather than scraped open so that little damage is done to the peel. Therefore, the amount of contaminating material washed away with the oil is minimal. This, in turn, makes the water stream separated from the emulsion cleaner and easier to recycle.
Water Oil emulsion
Fig 5.8 An oil extraction system.
The rollers conveying fruit are Pulpy juice placed in a water bath and the oil from extractors from the pierced glands is washed out with water. After a ﬁnishing (straining) stage to remove any large particles of peel, the oil-water Pulp emulsion can be concentrated and Finisher 1 Finisher 2 Pulp wash polished in a series of centrifuges production/ (see subsection 5.8 on peel oil refeed mill Juice Juice covery). The water is recycled to a large degree. Instead of more recently developed oil extraction system Clarifying centrifuge upstream of juice extraction, older installations incorporate peel shavers placed after the juice extraction stage. The outer layer of ﬂavedo is Product chiller literally shaved off from the peel mechanically. It is washed and pressed to remove the oil. The Buffer storage tank emulsion is then centrifuged in the conventional manner. The reamer-type extraction system requires two separate steps to extract juice and oil from the fruit. Concentrate production NFC production Nevertheless, the oil emulsion is often considered cleaner, easier to Fig. 5.9 The clariﬁcation process. centrifuge compared with other types oil recovery system, and the extracted juice has less contact with the oil. 5.4.4 DOWNSTREAM OF THE JUICE EXTRACTORS
5.5 Clariﬁcation The juice leaving the extraction process is clariﬁed as it contains too much pulp and membrane material to be processed in the evaporator or as NFC. Typical process steps in juice clariﬁcation are shown in Figure 5.9. Pulp levels in pulpy juice from the extractors are generally around 20–25 % of ﬂoating and sinking pulp. The juice is therefore ﬁnished, that is, pulp is removed from the juice. A ﬁnisher is basically a cylindrical sieving screen. There are two types of ﬁnisher – screw-type and paddle. Their operating principles are shown in Figures 5.10 and 5.11.
The juice streams leaving either a squeezer-type extractor line or reamer-type extractor system ﬂow to clariﬁcation and then evaporation, or pasteurisation if the end-product is NFC. The oil emulsion ﬂows to peel oil recovery for separation by centrifugation. Peel, rag, seeds and other solid material are conveyed to the feed mill.
The standard squeezer-type extractor includes a preﬁnishing tube in the extractor and the pulpy juice ﬂows directly to the primary ﬁnisher.
These include a stainless-steel screw that conveys the pulpy juice through the unit and presses the pulp against the cylindrical screen. The juice ﬂows through the screen holes. The pulp is consequently “concentrated” inside the screen and is discharged at the end of the ﬁnisher. As pulp is discharged through a restricted opening, the resulting back-pressure in the ﬁnisher helps to squeeze out more juice from the pulp mass.
Typically, the pulp content in juice leaving the secondary ﬁnisher is about 12 %. This pulp is predominately sinking pulp. If the market requires a juice with lower sinking pulp content, the juice can be further clariﬁed by centrifugation. A two-phase clariﬁer is normally used for this application. Separation in the disc stack centrifuge takes place in the spaces created between a number of conical discs stacked on top of each other to provide a large separation area. Most models rotate at between 4,000 and 10,000 rpm. The accumulated solids can be discharged, without having to stop the centrifuge, by rapidly opening an annular slot at the periphery of the rotating bowl. The clariﬁed juice leaves the centrifuge under pressure. Clariﬁcation by centrifugation often leads to improved operation of the evaporator system by providing consistent pulp levels in the juice. In order to meet recent demands for FCOJ with very low and low pulp content (