quality control of fish

TITTLE: QUALITY CONTROL TEST OF FISH

DATE

OF

EXPERIMENTS:30.07.2013 INTRODUCTION Freshness is one of the most important attributes of fish quality. It can be measured by different analytical methods. These methods can be divided into two categories which are sensory methods (quality index method) and instrumental methods (chemical, physical and bacteriological analysis). In addition, sensory method has been seen as subjective assessment of quality besides sensory test is still the most commonly used scale to grade the freshness of fish. Sight, smell, taste and touch of the fish represent the main components of this analysis. The sensory test can be divided into three groups which are discriminative tests, descriptive tests, and tests measuring the acceptance by consumers. On the other hand, other method of determining the fish quality is by objective method. One of the objective methods is using chemical where the evaluations of food using chemical methods are considered to be more objective than sensory methods. Chemical methods of food evaluation are normally used to predict the level of a sensory attribute, which allows for immediate determination of freshness. For example, Peroxide Value (Pv), Thiobarbituric Acid (TBA) and Iodine value (Iv) are also constitute to the chemical methods that are used to measure rancidity in fish and fish products. The freshness of the fish can also be determined by measured the amount of hypoxanthine (Hx) in fish. Besides that, physical method is also one of the instrumental methods which can determine the freshness of the fish. The examples of physical methods is by checking the pH and Eh of the fish, measuring the texture of fish flesh and electrical properties which measured the degree of spoilage and the changes of post mortem. For microbiological methods, the possible presence of bacteria or organisms of public health significance was evaluated. On the

other hand, microbial test was conducted to give an impression of the hygienic quality of the fish including temperature abuse and hygiene during handling and processing of the fish product. The example of microbial methods is by using total plate count methods. In correlated to sensory analysis, the score that was given is by using quality index method (QIM) where QIM is based on the significant sensory parameters for raw fish when using many parameters besides a score system is from 0 to 4 or by using a modified organoleptic quality index scheme demerit points. QIM is using a practical rating system, in which the fish is inspected and the appropriate score is given and recorded. The scores for all the characteristics are then summed to give an overall sensory score which called quality index. In contrast, each fish species has its own characteristic sensory attributes (flavour, appearance, odour, and texture) which change with time and temperature after harvest. In addition, to keep the freshness of the fish hence it is consider to be consumed by the customer, some methods are created to preserve the freshness of the fish during transporting, handling and presentation. This is because; fish are believed to spoil very easily. One of the methods to keep the freshness of the fish and keeping its quality is by caught fish alive until consumption. The fish need to be transported from very sophisticated systems installed on trucks that regulate temperature, filter and recycle water and oxygen. On the other hand, keeping the fish alive until consumption is also a common method in preserving the quality of freshwater fish. Moreover, chilling the fish with ice is also common method in order to preserve the quality and keeping the fish fresh. This is because, reducing temperature to about 0°C, the growth of spoilage and pathogenic microorganisms is reduced, thus reducing the spoilage rate and reducing or eliminating some safety risks. Besides temperature reduction also reduces

the rate of enzymatic reactions. In contrast, melting ice will keep the fish moist, prevents surface dehydration and reduces weight losses. As the usage of ice in the market in very convenient and ice is used to make fish safe and of better quality to consumers hence the quality and freshness of the fish was preserved. OBJECTIVE 1. To determine the quality control test of fish 2. To determine the quality of fish PROCEDURE a. Evaluation of raw fish

The raw fish was examined and an attempt was made to follow the spoilage by means of the following score shhet

The score that was consider appropriate for the examination was inserted

b. Evaluation of Cooked Fish

The centre cut from the fish was removed

The fish was washed by minimum water and it was transferred to a pyrex glass casserole

The water was not added and the fish was cooked in steam over boiling water in water bath for 35 minutes

The water bath was removed and the fish was examined by using following score sheets

RESULTS Score A 8 8 10 10 8

Fish Type: Raw B 10 8 8 10 10

Score

Eye Gills Skin Odour Texture

Fish Type: Cooked

A

B

8 8

10 10

Fish Odour Texture & Colour

DISCUSSION Freshness of the fish is the most important attributes in keeping quality of fish. From this experiment, the quality control of fish was determined by using two fish which is from Kembung species. The fish was bought in different day as type A fish was buy earlier than type B fish. Both of the fish was evaluate in two conditions which are raw and cooked in a steamer. As fish is easy to spoil the condition of the fish was measured by sensory analysis where the appropriate scores ranging from 0 to 10 was given in modified organoleptic quality index scheme that was given. Through the results, both fish was evaluated in raw condition by observing the eyes, grills, skin, odour and texture.

Type A fish that was

bought earlier than type B fish show that the eye of the fish is slightly sunken, slightly opaque and cloudy. While, the eyes of type B show perfectly black and transparent pupil than fish A. Hence, the score that was given to type A and type B fish was 8 and 10 respectively. On the other hand, grills of the both fish show some discolouration with mucus where appropriate score of 8 was given on both type of the fish. Different goes on skin of the fish where type A fish score 10 points for bright,

fresh

bloom

and

the

slime

was

transparent

characteristics.

Meanwhile, type B fish just score 8 point as the skin was bleach and dull and some opaque slime is present. On the other hand, both types of fish also score 10 points on odour as fresh and laky odour can be detected. Besides, the texture of the type A and type B fish score 8 and 10 points respectively. The score of type A fish was slightly less than type B because type A fish was fresh and laky while type B fish was neutral which are not stale and fresh. In contrast, fish that was cooked by steamer was also evaluated by removing the centre cut from the fish. Type fish A and B show slightly

differences in odour, texture and flavour. For type A fish, the odour of the fish show that some freshness are retained thus score of 8 was given for this type of the fish. While, type B fish score 10 points as fresh odour can be observed from this fish after cooked. In addition, the texture and colour of type A fish results in soft an dull where 8 points was given to this type of fish besides type B show firm, juicy and white in colour hence 10 marks was given to this fish. Through the experiment, fish B show some freshness than fish A. This is because some higher score that was given for type B fish during the observation of raw fish. Meanwhile, type A fish was also fresh but some of the characteristic such as eyes, grills and texture show slightly unfresh than type A fish as it was buy earlier than type B fish. As fish is easily to spoil, the fish should be put in refrigerator to reduce the temperature as it can keep the freshness of the fish and maintaining the quality.

STUDY QUESTIONS 1. Texture is an important property of fish muscle, weather raw or cooked. What causes fish muscle to become:  Tough After a fish dies, the flesh quickly becomes rigid and tough. This is a process known as rigor mortis. Rigor mortis is one of the one of the recognizable signs of death caused by a chemical change in the muscles and causing the limbs of muscles after death difficult to move or manipulate. When muscles contract, they absorb calcium ions. After a fish has died, calcium ions leak into the muscles, causing them to contract. However, ATP, the biochemical energy carrier that provides energy to relax the muscle again, is no longer present, so the muscles remain rigid. Rigor

mortis was also affected by several factors such as the handling, temperature and amount of struggle prior to death. 

Softy and Mushy

One of the reasons why the texture of fish become soft and mushy is because of the enzymes that present in the fish. Enzymes are naturally occurring chemicals that fish use for digestion and for muscle movement. After a fish dies, enzymes begin to digest the flesh causing the flesh to burn or become soft and mushy. One way this happens is that the natural sugars in the flesh are converted to lactic acid. This happens when the sugars are digested without any oxygen, or under anaerobic conditions. Besides that, overthaw frozen fish will also affect the texture of the fish. When thawed fish is warmed too much, spoilage is more rapid, and texture may be impaired. Thawed fish that left in water will rapidly become soft and mushy and will lose flavour as the flesh absorbs water.

2. Give 3 reasons why ice is utilized in fish preservation? 3 reasons why ice is utilized in fish preservation because the usage of ice can reduce the temperature that surrounds the fish. By reducing temperature to about 0°C the growth of spoilage and pathogenic micro-organisms is reduced, thus reducing the spoilage rate and reducing or eliminating some safety risks. Besides, temperature reduction also reduces the rate of enzymatic reactions, and extending the rigor mortis period.

Besides that, melting ice will keep the fish moist. This action mainly prevents surface dehydration and reduces weight losses. Melting water also increases the heat transport between fish and ice surfaces as the quickest practical chilling rate is obtained in slurry of water and ice. In addition, ice also has large cooling capacity as it maintained 0 degree Celsius although it changes from solid to liquid during melting of the ice. Moreover, the usage of ice can also extended the shelf life of the fish. The overall reason for icing fish is to extend fresh fish shelf life in a relative simple way as compared to storage of un-iced fish at ambient temperatures above 0°C. Besides, extending the shelf life, the usage of ice was also applied for producing safe fresh fish of acceptable quality. CONCLUSION In conclusion, for evaluation of raw fish, the eyes of the fish were given 8 and 10 points for type A and B respectively. Besides that, both type A and B fish score 8 points on grills. In addition, type A show 10 points for the skin while type B score 8 points. 10 point was also giving to the odour of the fish for both type A and B fish. In addition, type A fish score 8 point in texture and type B fish 10 points. Meanwhile, for cooked fish, the odour of the fish shows 8 and 10 point for type A and B respectively. Same goes to the texture of the fish where there is no bigger difference can be observed where type A fish scores 8 points while type B fish scores 10 points. Overall observation from this sensory analysis show that type B fish was slightly fresh than type A fish. REFERENCES (n.d.),

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