Pigment

Pigments Pigments are chemical compounds which reflect only certain wavelengths of visible light. This makes them appear "colorful". Flowers, corals, and even animal skin contain pigments pigments which give them their colors. More important important than their reflection of light is the ability of pigments to absorb certain wavelengths. Because they interact with light to absorb only certain wavelengths, pigments are useful to plan plants ts and and othe otherr auto autotr trop ophs hs-o -org rgan anis isms ms whic which h make make thei theirr own own food food usin using g photosynthesis. photosynthesis. In plants, algae, and Cyanobacteria, Cyanobacteria, pigments are the means by which the energy of sunlight is captured for photosynthesis. However, since each pigment reacts with only a narrow range of the spectrum, there is usually a need to produce several kinds of pigments, each of a different color, to capture more of the sun's energy.

NATURAL PIGMENTS: Natural pigments are those pigments which are derived from animal, vegetable, and mineral substances.

EXAMPLES OF

COLOUR PIGMENT

EC No.

Red/Blue

Anthocyanins

E 163

Pink

Betanin

E 162

NATURAL OCCURRENCE Black Grapes Blackcurrants Cherries Elderberries Red Cabbage Strawberries

Beetroot

STRUCTURE

Red

Carminic Acid

E 120

Green

Chlorophylls

E 140

Parsley

And

E 141

Spinach

Chlorophyllins

Cochineal

Alfalfa Grass Nettles

Carotenoids: Annatto

Yellow

Carrots

Orange

Oranges

Red

Mixed Carotenes

E 160a (i)

Prawns Red Peppers

Beta-Carotene

E 160a

Saffron

Bixin/Norbixin

( ii )

Tomatoes

Capsanthin/

E 160b

Palm Fruit

Capsorubin E 160c Lycopene

Apocarotenal

E 160d

Apocarotenal ( Ethyl Ester)

E 160e

Lutein

E 160f 

Canthaxanthin E 161b

E 161g

Turmeric

Yellow

Curcumin

Eggs

Yellow

Riboflavin

Milk Yeast

E 100

Carbonized Vegetable Material

Black

Carbon Black

E 153

Melanoidins

Brown

Melanoidins

E 150a-d

(Caramel)

Anthocyanins : • •

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Anthocyanins are water soluble pigments. They are responsible for the attractive red, purple and blue colors of many flowers, fruits and vegetables. They are sensitive to pH change, being reddest in strongly acidic conditions and become bluer as the pH rises. Chemically anthocyanins are subdivided into the sugar-free anthocyanidine aglycons and the anthocyanin glycosides. They are used as food additive with E number E163.

Structure: •

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Over 500 different anthocyanins have been isolated from plants. They are all based on a single basic core structure, the flavyllium ion. When anthocyanidins are coupled to sugars, anthocyanins are formed. As sugars can be coupled at different places and many different sugars are present in plants, it is clear that a very large range of anthocyanins can be formed. For example in strawberries the main anthocyanins are Cyanindin-3-glucoside and Pelargonidin-3-glucoside, two relatively simple structures.

Occurrence Occurrence and function: •

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Anthocyanins occur in nearly all plant families and thus in many edible plants. In food, the main sources of anthocyanins are berries, such as blackberries, grapes, blueberries etc, and some vegetables, such as egg-plants (aubergine) and avocado. Other sources include oranges, elderberry, olives, red onion, fig, sweet potato, mango and purple corn. The natural production of anthocyanins in nature is estimated to be 109 tones/year  Anthocyanins have many different functions for the plant. They are antioxidants, protect the plant against UV-light, are a defense mechanism and are of course very important in the pollination and reproduction. The colour of many flowers is due to anthocyanins, and thus is important in attracting insects. As anti-oxidants anthocyanins protect plants from free radicals (produced by sunlight or destruction of the plant), which may destroy the DNA, and cause cell death.

Anthocyanins content in some edible plants

Foodstuff

Anthocyanin in mg per  100 g food

aubergine (egg plant)

750

black currant

130-400

blackberry

83-326

Blueberry

25-497

Cherry

350-400

chokeberry

200-1000

cranberry

60-200

Elderberry

450

orange

~200

Radish

11-60

raspberry

10-60

red currant

80-420

red grape

30-750

red onions

7-21

red wine

24-35

Strawberry

15-35

Use: •

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Anthocyanins are water soluble strong colours and have been used to colour  food since historical times. Extracts of berries have been used to colour drinks, pastries and other foods. Grape peel (E163(i)), and black currant extract (E163(iii)) are the most widely used anthocyanin mixtures in foods.

Activity and toxicity: •

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Anthocyanins, when used as food colours, are not toxic and do not exceed the levels that may be ingested by consuming berries or other anthocyanin-coloured fruits. There are indications those anthocyanins as antioxidants have health promoting effects, which include reduced risk of coronary heart disease, improved visual activity and antiviral activity. However, many of these claims are not proven scientifically.

Disadvantages:

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Color is susceptible towards temperature, oxygen, UV-light and different cofactors. Temperature may destroy the flavylium ion, and thus causes loss of  colour. Temperature causes Maillard reactions, in which the sugar residues in the anthocyanins may be involved. Light may have a similar effect. Oxygen may destroy the anthocyanins, as do other oxidizing reagents, such as peroxides and vitamin C. Many other components in plants and foods may interact with the anthocyanins & either destroy, change or increase the color. Quinones in apples, for example, enhance the degradation of anthocyanins, whereas the addition of sugar to strawberries stabilizes the color.

Beetroot colors (betalai ( betalains) ns) The colour of beetroots is caused by the colours, betanin and vulgaxantin. Beetroot extract is used as a food colour and has E-number E162.

Structure: Betalains are classified on their structure and divided into two groups; betacyanins and betaxanthins, with red-purple and yellow colours respectively. More than 50 betalains have been described. In beetroot the main betacyanin is betanin and the main betaxanthins are vulgaxantin I and vulgaxanthin II (fig 3). The latter only differ in one side group of the molecule.

Betanin

Vulgaxanthin I (left) and II (right)

Use: •

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Beetroot extract or –pulp has been used to colour food for many centuries, but the beetroot itself always was an ingredient. The use of betalains as separate food colours date from the early 20 th century, when in the US pokeberry (Phytolacca Americana) juice was added to wine to

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enhance the colour. Nowadays only beetroot extract has been approved as a colour in most countries. All betalains are water soluble, which limits the use. Betalains are stable between pH 3.5 and 7.0 which covers nearly all foods, with maximum colour stability at pH 5.5. Betanin is susceptible towards light and temperature, which limits the use to fresh foods, foods packed under modified atmosphere, or foods that undergo no heat treatment. It is mainly used in frozen products (ice cream, yoghurt). Dry Betanin is more stable and it is used as a colour in instant foods powdered soft drinks. It is also stable in high sugar conditions and can thus be used in candies and fruit gels and fillings.

Cochineal, Carmine, Carminic acid (E120) Carmine is the name of the colour pigment obtained from the insect Dactylopius coccus (old name Coccus cacti), that lives on cacti from the genus Opuntia. The pigment can be obtained from the body and eggs of the insect. It is still used as an organic antrepellent. Carmine is the name of the pigment; the actual colour is carminic acid (C22H20O13):

Carmine Cochineal is one of the few natural and water-soluble colorants that resist degradation with time. It is the most light- and heat-stable and oxidation-resistant of all the natural colorants and is even more stable than some synthetic food colours. Cochineal it is neither toxic nor known to be carcinogenic. However, the dye can induce an anaphylactic-shock reaction in a small number of people, due to impurities in the preparation, not due to the carminic acid.

Use: • •

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Cochineal is widely used as a food colouring agent. Cakes, cookies, beverages, jam, jelly, ice cream, sausages, pies, dried fish, yogurt, cider, maraschino cherries and tomato products were brightened with it as were chewing gum, pills and cough drops. It is also have its application in alcoholic beverages and processed meat products.

Chlorophyll

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Chlorophyll is a green pigment found in most plants, algae, and certain bacteria. As all leaves and thus all leafy vegetables contain chlorophyll, it is one of the oldest and most widely consumed pigments in our diet. It has been in the human diet forever, so it is considered as one of the safest food components. Chlorophyll plays an important role in plants photosynthesis, the mechanism by which plants acquire energy. Purified chlorophyll is used as a food colour with E-number E140, the more stable copper complexes of chlorophyll are number E141.

Structure: Chemically chlorophyll is a mixture of several highly complex molecules, which consist of a ring structure (the porphyrin structure) with a central magnesium ion, and a long hydrophobic side chain.

Structure of the two most common chlorophylls Chlorophyll a

Chlorophyll b

Chlorophyll c1

Chlorophyll c2

Chlorophyll d

C35H30O5N4Mg

C35H28O5N4Mg

C54H70O6N4Mg

Molecular formula

C55H72O5N4Mg

C55H70O6N4Mg

C3 group

-CH=CH 2

-CH=CH2

-CH=CH2

C7 group

-CH3

-CHO

-CH3

-CH=CH2

-CH3

-CHO

-CH3

C8 group

-CH2CH3

C17 group

C17-C18 bond

-CH2CH2COOPhytyl Single

Occurrence

Universal

-CH2CH3

-CH2CH3

-CH2CH2COOPhytyl

-CH=CHCOOH

-CH=CHCOOH

Double

Double

Single

Mostly plants

Various algae

-CH=CH2

Various algae

-CH2CH3

-CH 2CH2COOPhytyl Single

Cyanobacteria

Characteristics Characteristics of natural chlorophylls

Source: Chlorophyll is mainly extracted from alfalfa (Medicago sativa), nettles (Urtica dioica) or  grasses. Chlorophyll can be extracted from the plants by several solvents, but has to be carried out rapidly in dim light to prevent degradation of the pigment. The resulting extract is further purified. Chlorophyll is not very stable, but stability can be increased by de-esterifying the chlorophyll and adding copper ions. These copper-complexes have a good green colour  and are more stable than natural chlorophyll.

Use: •

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Due to its safety, chlorophyll can be added unlimitedly to nearly all foods . It is mainly used in sugar confectionery and dairy products. Chlorophyll-coloured products should be dry and not exposed to light, air or high temperatures, In many cases the products are packed in dark packaging with a modified atmosphere to prevent chlorophyll degradation .

Carotenoids •

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Carotenoids are a class of natural pigments that is very widespread and it was demonstrated that they occur in all the three domains of life, i.e. in the eubacteria, the archea and in the eucarya. A rich source for carotenoids are the algae and more than 100 carotenoids have been isolated and characterized from these organisms. For humans the most important source for carotenoids are plants, where often the brilliant colours of the carotenoids are masked by chlorophyll, e.g. in green leaves. The carotenoids are responsible for the beautiful colors of many fruits (pineapple, citrus fruits, tomatoes, paprika, rose hips) and flowers (Eschscholtzia, Narcissus), as well as the colours of many birds (flamingo, cock of rock, ibis, canary), insects (lady bird), and marine animals (crustaceans, salmon). Normally carotenoids occur in low concentrations, but this varies enormously from one source to another. The total carotenoid production in nature has been estimated at about 100.000.000 tons a year.

Recently it was demonstrated by the analysis of serum and human breast milk that up to 50 dietary carotenoids from fruits and vegetables may be absorbed and metabolised by humans. Examples of carotenoids in common foods: Carrot In natural products the most common carotenoid is the yellow-orange pigment of  the carrot (Daucus carota), the ß,ß-carotene . It was isolated in crystalline form as early as in 1831 by •

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Average ß,ß-carotene content in mg/100 g edible portion of the fruits and vegetables mentioned: Apples

0,1

Parsley

4,9

Apricots

1,6

Peaches

0,5

Asparagus

0,5

Plums

0,2

Beans

0,4

Spinach

3,5

Broccoli- brokuly

1,5

Sweet potatos

5,9

Carrots

6,6

Tomatoes

0,5

Cherries

0,6

Watermelons

0,4

Chicory

1,5

Zucchetti

0,2

Chives

2

Melon

2

Cress

5,3

Mangoes

2,9

Kale

5,1

Structure of Carotenoids: α-carotene: present in carrots, most green plants.

ß-carotene: present in carrots and most other plants.

Lycopene: present in many plants, especially in tomato.

α-cryptoxanthin: present in many coloured plants, including maize and papaya.

Zeaxanthin: present in many plants, especially in maize

Use: •

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Carotenoids added as colorants to many manufactured foods, drinks and animal feeds, either in the form of natural extracts (e.g. annatto) or as pure compounds manufactured by chemical synthesis. The production of carotenoids by biotechnology is of increasing interest. Carotenoids are essential to plants for photosynthesis, acting in light-harvesting and, especially, in protection against destructive photo oxidation.

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The essential role of beta-carotene and others as the main dietary source of  vitamin A has been known for many years. More recently, protective effects of  carotenoids against serious disorders such as cancer, heart disease and degenerative eye disease have been recognized, and have stimulated intensive research into the role of carotenoids as antioxidants and as regulators of the immune response system.

Curcumin (Turmeric) Turmeric (Curcuma longa) is an important spice and colouring agent and has been used for more than 2000 years. Turmeric (Curcuma longa) is an important spice and colouring agent and has been used for more than 2000 years. The colour consists mainly of curcumin and is used as a food colour with E-number  E100(i), crude turmeric powder is E100(ii).

Structure: The main compounds in turmeric are curcumin and its derivatives demethoxycurcumin and bis-demethoxycurcumin. The latter differ from curcumin in that the CH 3-groups are removed. The ratio between the three pigments differs between preparations, but curcumin is present in the highest concentration and bis-demethoxycurcumin in the lowest concentratin.

Structure of Curcumin

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Curcumin is not soluble in water, but dissolves in oils and alcohol. It is quite stable and gives a bright orange-yellow colour to products. In Asian cuisine turmeric is mainly used as a spice, whereas in Western countries the main use is as a colouring agent Curcumin is not stable under alkaline conditions above 7.5, which do not occur in many foods. Curcumin is light sensitive but stable at temperatures used in food processing. Light sensitivity is decreased by the addition of aluminum ions, which form a complex with curcumin and thus protect degradation by light. Turmeric and curcumin are widely used in foods and cosmetics. Applications include canned beverages, baked products, dairy products, ice cream, yoghurts, yellow cakes, biscuits, popcorn-colour, sweets, cake icings, cereals, sauces etc.

Flavonoids The flavonoids are polyphenolic compounds ,with structure similar to those of  anthocyanins and also occur as glycosides.Flavonoids differ from anthocyaninin having

a carbonyl group in position 4.These include the groups of  compounds,flavones,flavonoids,flavonols,flavanones(and isoflavanones),chalcones,aurones and biflavanyls.

Flavone

Flavonol

Flavanone

Good sources of flavonoids include all citrus fruits, berries, ginkgo biloba, onions, parsley, pulses,tea (especially white and green tea), red wine, seabuckthorn, and dark chocolate (with a cocoa content of seventy percent or greater).

The citrus bioflavonoids include hesperidin (a glycoside of the flavanone hesperetin), quercitrin, rutin (two glycosides of the flavonol quercetin), and the flavone tangeritin.The citrus bioflavonoids include hesperidin (a glycoside of the flavanone hesperetin), quercitrin, rutin (two glycosides of the flavonol quercetin), and the flavone tangeritin. Green tea flavonoids are potent antioxidant compounds, thought to reduce incidence of  cancer and heart disease. Flavonoids exist naturally in cacao, but because they can be bitter, they are often removed from chocolate, even the dark variety.

Riboflavin Riboflavin, Vitamin B2, is used for fortification and colouring. It is water soluble, heat stable and is used in dairy products, cereals and dessert mixes

Carbon and metals Vegetable carbon black is a heat and light insoluble pigment, used primarily in sugar  confectionery. Metals, such as gold, silver and aluminum are used for surface colouring, mainly in confectionary.