GITAM INSTITUTE of SCIENCE, GITAM UNIVERSITYDepartment of Microbiology and Food Science & Technology

Lecture-in-charge : Ch. PadmavatiDate : 06/06/2017

Name of The Student

Jyotshana hanumantha

Registration Number

1223616119

Course M.Sc. Food Science and Technology

Year and Semester

1st Year 2nd Semester

Subject Technology of Animal Foods

Unit and Topic Unit-V, Fish and Marine Foods- Quality of Fish

Fish and Marine Foods : Quality

of Fish

Introduction After independence, India has made glorious achievements in food production and have witnessed multicolor revolutions in terms of green, yellow, white and blue. As compared to food grains, milk eggs and other foods, country’s fish production has increased at a higher rate. This sector is contributing 1.2% to the national GDP and 5.3% to the agricultural GDP. Fish is a highly perishable commodity requiring a cautious handling and careful processing. To ensure best quality, appropriate technologies and processes must be followed with clean and hygienic conditions.

Keeping Quality of Fish The physical, chemical and bacteriological characteristics of fish are influenced by the species, seasons, catching methods and fishing grounds etc. The characteristics of fresh fish are- Shining, iridescent surface covered with a nearly transparent, uniformly and thinly spread slime. protruding eyes with a jet black pupil and transparent cornea gills that are bright and free from visible slime flesh is soft and flabby, tending to retain finger indentations the flesh odor is ‘marine’, ‘fresh sea weedy’ or laky in addition pleasant, margarine like odor in case of fatty fish

As the spoilage is developed in fish- its structure loses bright sheen and color and slime becomes thicker, turbid and lumpy lately, Slime becomes yellow or brown eyes sink and shrink with cloudy and milky pupil and opaque cornea gills become bleached, light pink in color, finally turning to grayish brown covered with a thick slime. flesh becomes soft and inelastic and may be easily stripped from backbone and extrudes juice under light pressure. odor changes from ‘sweetish’ then ‘ammoniacal’ or ‘fishy’ and finally putrefaction odor.

Causes of Spoilage The fish spoilage may be caused by 3 causes-a) Bacteriab) Digestive enzymesc) Others such as oxidation, etc. The flesh of freshly caught fish is sterile while the spoiling microflora is present in external slime and digestive tracts. Fatty fishes may develop spoilage due to all 3 above mentioned causes. If not gutted soon after catch, strong digestive enzymes affect the viscera and belly walls and cause discoloration- ‘ belly bum’ or disruption- ‘ torn bellies’.

Handling of Fish

• Handling of market fish Fish should be purchased as fresh or frozen as possible. Exposure to unsafe temperature should be avoided. Exposure to contaminants should be avoided by keeping fishes in plastic bag. It should be kept in refrigerators at home. Raw fish purchased should not come in contact with cooked fish, other cooked food stuffs and raw fruits and vegetables as raw fish contains bacterial load. It should be stored at proper temperature- if hot, temperature should be 140ºF and if to be kept cold, temperature should be 40ºF or less.

• Handling of fresh catch Efforts should be done to keep the fish alive as long as possible- by keeping in metal link basket or live box. The fish should be checked for signs of disease or parasites or for any abnormal growth in the flesh. It should be made certain that the fish is being taken from safe water without any contaminants. If it is difficult to keep fish alive, it should be stored at temperature below 40ºF.

Gutting, Cutting and Cleaning

The harvested fish should be cleaned and cooled as soon possible due to their strong digestive juices, fish spoil very soon and if not gutted and cleaned promptly may develop off flavour and color.

A sharp knife, clean cloth, plastic bags and crushed ice must be kept ready for gutting and cleaning of fish.

With the help of knife, fish should be cleaned and bled. Throat should be cut and gills and entrails are removed. Cleaned fish first be put in plastic bags and then in ice. To prevent contamination, hands, working area, cutting boards, knives

and other utensils should be properly cleaned with water and soap.

Preparation of Fillets

Wash the fish in clean cold water to remove blood, microbes and enzymes.Filleting is done with a sharp knife with flexible blades.The fillets collected should be stored properly at low temperature.

Process of Filleting• Fish is cut behind the pectoral fin straight down to the backbone and cut is angled towards the top of the head

• ↓• Knife is run along one side of the backbone, scrapping the rib bones without cutting them

• ↓• The knife is pushed through the flesh near the vent just behind the rib bones and fillet is cut free at the tail

• ↓• Flesh is cut carefully away from the ribcage.

• ↓• The first boneless fillet is removed by cutting through the stomach skin.

Storage• After cleaning and packaging the fish should be stored either by refrigerating or freezing.• Refrigerating- Raw fish can be kept in refrigerator at the temperature of 40ºF or lower. Should be stored in covered containers. While keeping in refrigerator, fish should be moist but not wet. For refrigerating fish at home, the fish should be removed from wrapper, rinsed properly in clean cold water, pat dried with paper towel and kept in a plate or pan lined with double layer of paper towels. The pan should be covered tightly with aluminium foil or plastic wrap to avoid leakage. This covered fish may be kept in the coldest part of the refrigerator.

• Freezing- It is done if the fish is not to be used within 2 days of the catch or to be transported. It must be properly cleaned and handled before freezing. The temperature of freezing fish should be 0ºF or less. Following methods can be used for freezing the fish-A. Double wrapping- Suitable for small whole fish, steaks or fillets. In this, fish is tightly wrapped individually in plastic wrap and again wrapped tightly with another layer of wrap. These wrapped pieces are kept in a sealable freezer bag or may be wrapped tightly in aluminium foil. The sealed bags are placed scattered in freezer and when they are frozen, they can be stocked on top of each other.

B.Freezing in ice block- This method is suitable for steaks and fillets. It protects the fish from freezer burn and avoids the exposure from air. For freezing fish in ice box, it is cut into small pieces and placed in containers. Head space of one inch should be left for expansion. Fish is then covered with cold water and kept in freezer to freeze. Check whether fish is completely covered with ice or not. When freezing is done in a pan, the ice block is taken out by running little cold water at its bottom and ice block is double wrapped and kept in freezer.

C.Glazing- This method is suitable for whole fish or large cuts. In this method, fish is first frozen by placing them on a baking sheet in a single layer and the frozen fish is then dipped into a container having ice water and allowed to freeze again. This process is repeated until an ice coating of at least 1/8” thickness is made on the fish. It is then put in an airtight freezer bag or container and kept in freezer. At interval, glazing should be checked.

Care during Freezing The package should be marked with content and date. Wrapped package should be sealed tightly. When fish is frozen, make sure its fully covered with ice. Frozen fish brought from market should be put in the freezer at the earliest and in the original package only. Putting the fish package in freezer bag before keeping in freezer to provide an extra protection.

Points to remember during storage of fish

Fish must be cleaned thoroughly. Refrigerator temperature should be 40ºF or low. Thawed fish should not be refrozen again. Thawing should be done in refrigerator or cold water that must be changed at every half an hour. Fish should be frozen as soon as possible after the catch. The package should be mentioned with content and date.

CONCLUSION

Fish is a highly perishable product and can be handled safely to improve its shelf life. Different processing methods like canning, drying, smoking, etc if applied properly to the fish as soon as the fish is caught, can enhance the shelf life from months to years depending on the methods used. The processed fish can be transported to the distance places without the risk of spoilage and food poisoning.