BY-PRODUCTS AND VALUE ADDITION OF FISHES

Fishes are consumed as food in fresh condition. Some of them are also utilized after the preservation. During preservation and processing, some materials of fish and prawn are discarded as waste. Similarly some trash and distasteful fishes are unsuitable for human consumption. These waste material and above fishes become an important source to produce fish by-products, which in turn are used to produce different useful fish by-products.

FISH PROTEIN CONCENTRATE

Fish protein concentrate (FPC) is a stable protein concentrate prepared from whole fish or other aquatic animals or parts thereof. Protein concentration is increased by removal of water, oil, bones and other materials. Traditionally dried or otherwise preserved products do not fall within this definition. Development of FPC has paved the way for converting a wide range of whole fish into protein concentrate, which has no resemblance to the original raw material, for human nutrition.

Proximate composition

Fish Protein Concentrate is a gritty, colourless, odourless and tasteless powder. It is stable up to 3-4 years at room temperature without any significant change in flavour. Proximate composition of a representative sample of FPC is given below:

The greater quantity of highly digestible protein, available lysine and minerals makes FPC a highly nutritious product.

Though FPC is intended for human consumption it is not relished for consumption as such. It is therefore incorporated as a protein supplement in human diet. 5-10 per cent level FPC in bread and biscuit is considered the acceptable limit. 35 g per person per day is a recommended level of use of FPC.

Fish undoubtedly is one of the most nutritious foods available for human consumption. Fish flesh on an average contains 15-20 per cent protein. Some species of fish contain very high amounts of body oil. Few species of fish like shark, cod etc. are good sources of liver oil. Fish processing and filleting industries turn out large quantities of fishery waste. All these are good sources of high quality protein, fat, minerals etc.

The traditional fishery byproducts are fishmeal, fish body and liver oils, fish maw, isinglass etc. Fish protein concentrate, fish albumin, glue, gelatin, pearl essence, peptones, amino acids, protamines, fish skin leather etc. are some other byproducts generally processed out of fish and fish waste. Chitin and chitosan processed out of shrimp, crab and other crustacean waste are byproducts of high economic value. Biochemical and pharmaceutical products like bile salts, insulin, glucosamine etc. are some other fishery byproducts of great significance. A brief account of some of the important fishery byproducts is given below.

1.  GELATIN

Gelatin is a protein that lacks in an essential amino acid tryptophan, and hence cannot be considered as a sole source of protein in animal or human nutrition. But it is a relatively high source of lysine and methionine, which are deficient in cereal proteins. However, gelatin finds extensive use in food as also in the formulation of some industrial products. Gelatin can be extracted from the skin and bones of fish.

 Uses

Gelatin is used in the food industry as a gelling, stabilising, emulsifying, dispersing or thickening agent.

2.   INSULIN

Insulin is a hormone used for correcting the condition called diabetes mellitus in humans. Fish insulin is more stable as it is not subjected to decomposition by protein splitting enzymes of pancreas.

Fish albumin is a product similar to egg albumin in physical and chemical properties. It can be processed out of proteinaceous residue from fish scrap or fish waste. Two grades of fish albumin are produced, the technical grade and the food and pharmaceutical grade.

 Uses

Fish albumin is widely used in food and pharmaceutical products as whipping, suspending or stabilizing agent. 
Food grade albumin is an additive in ice cream, soup powder, puddings, confectionery, bakery products, mayonnaise, custard powder etc.

MINCE AND MINCE-BASED PRODUCTS

Fish mince or minced fish is the flesh separated from the fish in a comminuted form free from scales, skin and bones. Trimmings from the fish filleting operations, whether hand or machine filleting, was the original source of fish mince. Significant value addition will accrue to such fish if converted into fish mince because mince can be used to process a variety of value added products having high commercial potential. Another advantage of the process is that it conceals identity of the original fish from which it is made and consumers may not hesitate to accept mince or mince based products even though the original fish would have been unacceptable as whole fish.

PRODUCTION OF FISH MINCE

Mince can be prepared either from gutted fish or whole fish. Mince from gutted fish will be better in colour, appearance and flavour. For best quality minces it is desirable to use only a single species of fish so that mince of different quality and stability do not mix together.

The freshness of the raw material profoundly influences the quality of the mince. The mince will contain all the components like the enzymes, lipids, haem pigments etc. in the fish that affect its shelf stability. The mince is frozen and stored.

MINCE-BASED PRODUCTS

The fish mince finds application in processing several convenience foods like fish finger, cutlet, burger and also in some low cost salted and dried products. In preparation of fish finger, stick, sake etc., the mince stripped from the bone frame is incorporated to increase the yield.

Fish finger

Fish finger is a very popular product made out of fish mince. The mince is mixed with 1.0 per cent salt, made into rectangular slabs and frozen. The frozen mince is cut into suitable uniform sizes. These pieces are given a coating of batter followed by breading. The battered and breaded fish fingers are flash-fried in oil maintained at 180-200° C for about 20 seconds. After cooling the fingers are frozen and stored.

Fish Burger

Burger is made using mince from lean white fleshed fish. Cooked mince is mixed with cooled potato and mild spices and formed into flat round pieces. These are battered, breaded and flash-fried as for fish fingers.

Salted Fish Cake

The mince is mixed with salt. Salting will denature the protein and reduce its water holding capacity and hence will result in release of water. The fish/salt mix is pressed suitably to release more water. The resultant cake is dried.

Several other products like cutlet, fish ball, paste etc. can be processed out of fish mince.

CANNING OF FISH AND FISH PRODUCTS

Canning is a method of preservation of foods in which spoilage is averted by killing the microorganisms present by application of heat and preservation of subsequent contamination, the product being enclosed in a hermetically sealed container.

High acid foods like fish marinades and pickles containing acetic, citric or lactic acid do not support the growth of bacteria and hence spore-forming pathogenic microorganisms will not grow in them. Therefore such foods need heat processing only at 100°C or below.

Fish packed in tomato sauce is a medium acid food. Such foods will require heat processing sufficient to make them safe against C. botulinum.

Canned fish in general, except when packed in medium like tomato sauce, is a low acid food and often will have a pH close to neutral. Therefore canned fish will require heat processing as do low acid foods to ensure safety against C. botulinum.

 Fish oils

The oils from the fish are obtained by extracting from the entire body of the fish or only from the liver. The oil obtained from the entire body is known as body oils and are grouped into drying and semi drying oils. The drying oil comprises oils of sardine, salmon, herring, mackerel, anchovy, and white fish, while the oils of sprat and carp constitute semidrying oil due to the low iodine content. The body oil is edible and used for industrial purposes. Liver oil extracted form the liver, is of medicinal importance and contains vitamin A. Freshly extracted oils are differently coloured from colourless to golden yellow, greenish yellow or even red. The oil extracted from the stale fish is darker in colour and concentration of the oil also varies from fresh to stale along with iodine content.

 Liver Oil

Fish liver oil consists of vitamin A mainly and vitamin D in some species. These vitamins may be formed due to metabolic activities which might have been made their way into the liver and to be stored. Vitamin A mainly gets stored in the liver. But in large fishes this vitamin gets accumulated in viscera also in addition to liver. The dark coloured liver in sharks yields higher concentration of vitamin A than the light coloured ones. Vitamin A content of liver lobes are varied markedly in different lobes. Some fish liver oils are rich in vitamin D. Tuna liver oil and cod liver oil contain 2,50,000; 500 units per gram of oil respectively. Vitamin E in liver oils protects any oxidation of vitamin A.

Cod liver oil

Cod liver oil is obtained from different types of cod fishes like Gadus callarius and Gadus morrhua and other cods. Vitamin A in the oil gets destroyed when exposed to sunlight and the oil becomes thicker when exposed to air. Hence, the oil should be properly stored to avoid the destruction of vitamin A by addition of certain preservatives like nordihydrogualaretic acid (0.05%) and ascorbyl palmitate (0.01%). In view of rich concentration of vitamin A and D with digestible fat, it is found to improve nutrition and calcification in patients with rickets and tuberculosis when used. It can also be used as supplement for children and can be applied to wounds and burns.

Shark liver oils

Sharks of Indian waters except few are considered highly important from the yield point of oil from liver which consist of high vitamin A potency. (av. 12,000 IU/g of oil). Oils as rich as 3,00,000 IU/g. have been obtained. The freshly extracted oil is yellow, orange or brown in colour with mild fishy odour, and low acidity. The dilute shark liver oil is prepared by the addition of refined groundnut oil with vitamin D.

Fish flour

Fish meal is prepared by solvent extraction process on commercial scale. This can be blended with wheat or maize flour and is used as enriching component in bread, biscuits, cakes, sweets and soups. It forms an ideal protein supplement to human diets.

Fish flakes/wafers

Thread fin breams and cat fishes are used in the preparation of flakes or wafers. Fish flesh is boiled, mixed with maida, salt, etc. to prepare flakes or wafers.

Breaded prawns and fish sticks

Body shell and digestive tract are removed from prawn body and boiled for 15 minutes in 7 per cent salt solution. Fishes are cleaned and cut into 10 cm length and 1 cm width pieces. These are dipped in egg, maida, salt mixture, and then are added to bread powder to prepare sticks.

Fish salads

The fishes are cleaned and pieces are boiled with steam. The boiled fish or prawns are mixed with tomatoes, salt, garlic, maida, pepper and oil to prepare fish salad. This can be used in fresh condition or can be stored.

Fish sausage

Fish flesh is ground and mixed with sugar, fats, masala and preservatives. Small bags are prepared with above mixture and boiled to prepare fish sausage.

Fish cakes

Tuna and mackerels are used commonly to prepare fish cakes. Fishes are cleaned and steam boiled, then separated in layers. Potatoes are boiled with salt, pepper and citric acid. Layered fish are mixed with the above mixture and packed in vacuum to prepare fish cakes.

Fish proteins

The proteins of the fish have high digestibility, biological and growth promoting value. Hence, it plays an important role in human nutrition. The available amino acids are more evenly balanced than the other proteins of animal origin. Amino acids like lysine and methionine are rich in fish protein. In general, fish protein is somewhat superior to egg albumen, bean protein and casein and perhaps equal to chicken proteins.

15 - 25 per cent of protein is obtained from the fish muscle which forms the chief source. The fish proteins are extracted with dilute caustic soda solution from fish fillets or waste after removing the fat. The extracted material is dried after neutralization. This powder is white in colour without any fishy odour and taste containing 80 - 90 per cent of solubilized protein. This is used as a substitute for white of the egg in baking, confectionary, ice cream and pharmaceutical products.

Shark fins

The fins of the large sharks except caudal fin are cut near the root, washed in seawater, mixed with wood ashes and lime and dried in the sun or smoked. This product which is crisp and brittle are used in soups and regarded as delicacy.

SOURCE

http://bieap.gov.in/capturefisheriesandpostharvesttechnology.pdf