Fish spoilage and preservation - FOODZAQ

Hello friends, Welcome back to my blog FOODZAQ. Today we are going to discuss about Spoilage and preservation of fish. Spoilage of fish is mainly due to action of bacteria and enzymes. Oxidation of fat also leads to spoilage of food. The spoilage of fish can be identified by using organoleptic and microbial tests.

SPOILAGE OF FISH

The spoilage of fish is caused by bacterial enzymatic and oxidation of fat. Fishes are highly perishable food category which will easily spoil or less stable because of their high moisture content. 

Evaluation of freshness and spoilage

Organoleptic or sensory test such as assessment of quality by  appearance, color of guiles, eyes, fairness, texture and smell of fish are the sensory test carried out to evaluate the degree of spoilage. 

Different storing points are given for these tests. Analytical tests such as estimation of tri methyl amine nitrogen, total volatile nitrogen and peroxide value are also done for fish. Microbial methods like total plate count (TPC) is also used to determine the spoilage in fish.

• Skin and color will be bright and shiny for fresh fish. But spoiled fish has faded color.
• In fresh fish, scales are tightly attached, but scales will be loosen for spoilage fish.
• In fresh fish eyes are clear and not shrunken or wrinkled. In spoiled fish, eyes are cloudy, wrinkled and shrunken.
• Fresh fish is firm, while spoiled fish is soft.
• Spoiled fish produce off flavor.

Action of enzymes and spoilage

Enzymes are present in visceral digestive tract in the fishes and it also produced by bacteria. If visceral and gut bacteria are allowed to break down of fish tissue, they will be spread out of the gut, attack other areas of fish and lead to belly bust, which is a sign of spoilage.

Fish fed heavily before capture is increases the chance of belly burst. The break down of tissue will effect the flavor, texture and sometimes appearance of fish. 

Action of bacteria and spoilage.

When the fish dies, bacteria present in the body surface, guiles and in guts. Rapidly multiplied and make a ideal medium for growth and multiplication of micro organisms. At favorable condition, the growth of bacteria will double for every 20 minutes. Various types of bacteria are usually responsible for fish spoilage. This spoilage may lead to heavy slime on skin and unpleasant smell. Belly burst may also occur.

Spoilage  due to oxidation of fat

The oils and fat react with oxygen in the air and fat produce rancid odor, off flavor and color changes due to the production of some peroxide, ketones and aldehyde. In fatty fish, the chance of spoilage is high due to high percentage of fat content.

PRESERVATION OF FISH

Refrigeration or Chilling

Lowering the temperature to about 0C and it is the most effective method to prevent spoilage. Large amount of ice is used to lower the temperature of fish. Alternative layer of fishes and ice must be arranged to bring down the temperature of fish about 0C.

Freezing

Freezing arrest the growth of micro organisms and activity of enzymes partially or completely by converting fluid in the product in to ice. The water in fish begins to freeze at -1C itself. Types of freezers used in fisheries are listed below

• Airoblast freezer
• Contact freezer
• Immersion freezing

Smoking

Smoking is a method of preservation of fish and it provide more flavor to fish. Smoke contain several compounds which have preservative properties. Presence of some antioxidants and bacterial compounds in smoke will prevent the development of rancidity and arrest microbial growth. 

 Chemicals used for smoking are

• Phenolic compound : Increase color, taste and odor.
• Guacinol and phenol : Provide anti oxidant property.
• Formaldehyde : Preservative action.

Fish can be kept in trays which are loaded on trolley and kept in smoking chambers.

Pickling

It is done to enhance their keeping quality. Pickling protect the food and helps to retain whole sameness and nutritive value. Pickling is the use of a solution contain salt, vinegar and spices to care the food and periods of curing depends upon type of material used for pickling. Vinegar contain 4% CH3COOH is used. Vinegar provide inhibit the growth of bacteria.

Processing of pickling is describe below :

1. Selection of good quality fish.
2. Washing
3. Slicing or cutting of fish.
4. Mixing with water (brine) and keep for 2 hours.
5. Drying
6. Shallow fry in oil
7. Fry the ingredients.
8. Addition of spices.
9. Remove flame and add fry fish and mixing
10. Cooling
11. Add vinegar and powdered cardamom, clove and salt & mix thoroughly. 
12. Boiled and cooled water added to cover ingredients level.
13. Transfer to sterile, clean bottle.
14. A layer of oil is poured to pickle.
15. Storage

Canning of fish

Canning is the process of filling of food stuff inside a hermetically sealed container and apply thermal processing. The procedure for canning of fish is describe below.

1. Selection of fish.
2. Washing is done to prevent spoilage by using clean water.
3. Pressing and cutting. This include removal of bones and skin.
4. Braining : Immersion in salt solution for flavor and preservative action.
5. Pre cooking for 45 minutes to increase firmness.
6. Filling.
7. Exhausting.
8. Seaming.
9. Thermal processing at 121C for 15 minutes.
10. Cooling.
11. Labeling
12. Storage

Drying

Fish can be dried artificially or even through sun drying by spreading in sunlight. Artificial dehydration have several advantages of other conventional method. drying is quicker and more efficient. Contamination by dust, insect, birds, microbes and animals are avoided and form hygiene products. Hot air dryer, cabinet dryer and rotatory dryer are normally used. 

Guys, Thank you for reading my blog FOODZAQ. I hopes you should understands about Fish spoilage and preservation. If you have any doubts or query please feel free to comment below. If you like my blog, you can also read my previous blogs on food preservation. Thank you again. Have a nice day.