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Fishery Byproducts: A New And Promising Technique Of Commerce

Adita Sharma1 and Amita Saxena2

M.F.Sc Student, Dept. of Fishery Biology, Prof. Dept. of Fishery Biology

College of Fisheries, G. B. Pant University of Agriculture & Technology, Pantnagar — 263145 (Uttarakhand)

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Fish is a highly perishable food material because of its moisture and nutrient contents, and spoilable begins as soon as fish dies; it is the result of a series of complicated chemical reactions taking place in a dead fish, mainly by enzymes and bacteria. India's marine fish production has now crossed one million tone marks. Of this, Trash fishes constitute more than 40 %. These are either thrown back into the sea immediately after their catch or utilized wholly or partly as manure. If this fraction is used in the preparation of many usable by products, it would certainly augment our foreign exchange earning. The modern fish processing industry in our country is four decades old. Although we have exported dry fish and prawns during pre indepence; the export of marine products rose to 5 lakh tones worth Rs 6,500 crore in 2003. These phenomenal increases in export of marine products and development in the fish processing industry has been more or less based on a single commodity, prawns which constitute about 10-12% of the total marine catch. However, this modern trend is not so apparent in various other fish products and by products. One of the important by products of commercial value is fish meal, produced mainly from underutilized fish species and by-catch fishes.

Shark fins

The commercial value of the fins depends on their color, size, variety and quality. Depending on the quality and quantity of rays present in the fins they are broadly classified into 2 verities, generally known as black and white. Black fins usually fetch a lower price than white fins. The translucent cartilaginous rods embedded in the fins of shark are the fin rays used in the preparation of shark fin soup. These rays can be extracted from both freshly cut as well as dried fins. The latter are soaked in water which is acidified with acetic acid with pH 2.5 to 5 for 2-3 days while freshly cut fins require less soaking time. The softened fins are then treated with hot 10% acetic acid at 60°C for an hour depending upon their size. The rays are separated manually, washed well and dried in the sun. The dried rays which can have a moisture level of 5-8% are stored in polyethylene bags. The shark fin soup is considered as a delicacy in countries like China, Philippines, Hongkong, Singapore, etc. shark fins are in great demand particularly among Chinese, for making ceremonial dish called shark fin soup.


Chitin meant for deacetylation to chitosan is to be either dried or centrifuged or pressed well to remove as much water as possible. The left outs of prawns prior to their freezing in the processing factories such as their head and shell wastes are now used mainly as manure or as a source material in the preparation of feeds. From these wastes, chitosan, a valuable by deproteinisation, deminerlisation and deacetylisation. In the deproteinisation, the prawn wastes are first washed and heated with 3% sodium hydroxide solution for one hour in order to remove the crude protein content of these wastes. Subsequently, it is wasted well and transferred to a vessel containing 5% hydrochloric acid which removes the mineral content of the wastes in a period of about 30 minutes. This process is known as demineralization. The product so obtained is chitin which contains 60% moisture. The chitin is then subjected to deacetylistaion. In this process, the chitin is wasted well and heated with 40% sodium hydroxide solution for about one and half hours. Then the material is washed well, sun dried and pulverized. The resulting chitosan should be packed in polyethylene bags and stored at ambient temperatures. Chitosan is now a day's used as a valuable coagulant aid in the treatment of sewage, etc. it is also used as an additive in the baby food formulations; treatment of wounds; paper and textile industries and in photography.

Fish oils

Fish oil is two types viz. fish body oil and fish liver oil. In India fish body oil is mainly prepared from the oil sardines belonging to the species sardinella longiceps and fish liver oil from shark, skate, tuna, ray, etc. shark liver forms a very rich source of vitamin A and D. In India, at present the products are prepared at Kozhikode, Trivandrum and Bombay centers. The efficiency of extraction is more in the alkali digestion method. The fresh or preserved liver are washed and weighed. Then the associated structures of livers such as gall bladder and veins are removed and washed again. Subsequently livers are cut into pieces to which sufficient quantity of water is added and mixture is digested at 40-45°C till all the solids of the liver are liquefied. The digestion is also continued with 1-2% sodium hydroxide at 40 to 90°C. The pH is adjusted to 8 to 9 with HCL or H2 SO4 solution with constant stirring. To the cooled emulsion 3 volumes of 5% saline solution are added. Afterwards, it is centrifuged and washed in warm water. The separated oil is mixed with about 5 to 10% anhydrous sodium sulphate and is left undisturbed overnight. Finally, the product is filtered and stored in suitable airtight containers. Fish body oils are used in the manufacture of detergents, rubber, lubricants, printing links, leather and cosmetics. The weight of liver, fat content and presence of vitamin are dependent on a number of factors like species, age, sex, nutritional status of spawning and area from where it was caught.

Fish meal

Fish meal is a nutritious feed supplement consisting mainly of proteins, minerals and vitamins. Trash fishes such as leiognathids, lesser sardines and anchovities and fish wastes are commonly used for the production of fish meal through wet reduction process. In this process, the aforesaid source materials are ground and cooked. This would facilitate coagulation of protein and release of water and oil. Afterwards pressing is done to separate water and oil. The liquid portion is known as press liquor which is passed through a screen to remove solid particles of fish. Afterwards these particles are returned to the press cake. After drying the press cake, it is ground well and packed in polyethylene lined gunny bags. Constituents of meal vary depending on the type of raw material and the process used. Protein is generally around 65%. Moisture, fat and ash content vary at 6-10%, 5-10% and 12-33% respectively. Fish meal is also an important source for minerals such as calcium, phosphorus, copper, zinc, manganese, iodine and selenium. Hence fish meal is considered to be a valuable constituent of fish and poultry feeds.

Fish glue

Thick and firm skins of certain fishes are generally suitable for the preparation of fish glue owing to their good collagen content. However, low fat content of skins is desirable for the preparation of quality fish glue. The skin is washed and soaked in freshwater to remove salt or dirty substances. After soaking, they are cut into pieces and transferred to lime liquor which help to open the fiber bundles. After washing, the limed skin pieces are bated to remove lime. Afterwards, it is cooked in steam cooker and small amount of acetic acid which acts as a catalytic agent is added to hasten the hydrolysis. Then the glue liquor is drawn and evaporated until the liquid contains 50-55% solids. Afterwards, it is cooled below 15°C in a cooling box for 12 to 18 hours to coagulate. The coagulated jelly type glue is cut into moderate sizes and then drier. Any one of the antiseptics such as boric acid, salicylic acid or benzoic acid is added to liquid glue in order to conserve the product from spoilage. It is used for fixing wood, paper and leather. It is also used in book binding and labeling.

Fish protein concentrate (FPC)

It is a colourless and odorless power with highly concentrated animal protein and minerals. It is also known as fish flour, or edible fish meal. In its preparation, the minced meat is cooked with an equal volume of 0.5% acetic acid and is allowed to settle. The oil which floats on the surface is removed. The slurry is filtered through canvas bags and it's pressed. The pressed cake is treated first with ethanol to remove both moisture and odour and then with azeotrophic mixture of hexane and ethanol. The treated mixture is subsequently filtered, pressed and dried under vaccum. Finally it is pulverized and packed.

Fish pulp

Sardines, mackerel, sciaenids, etc., are used in the preparation of fish pulp. The meat is separated first from the skin and bones of selected and leaned fish and is treated with powdered salt. The brine that appears in a duration of about 6 hours in the above mixture is removed by pressing the meat, thereby the moisture content of the fish is reduced to 40%. Removal of the brine and the associated pigment help to increase the quality and shelf life of the product. The minced fish meat is then covered again with salt and kept in a hermatically sealed plastic container and stored at room temperature. The high salt content (24%) and intermediate moisture level of the product (50%) inhibit the development of micro organism, thereby the shelf life of the pulp is retained for six months without any preservative. The fish pulp is known to be a good and protein rich food source for the people of many developing contries although it has not yet become popular in India.

Fish sauce

Fish sauce is obtained from the mixture of fish and salt(3:1) which are fermented in wooden vats or concrete tanks. Generally trash fishes and cannery wastes such as head, viscera, fins, etc., could be used in its preparation. After the fermentation period or about six months, the supernatant liquid i.e. fish sauce is decanted and used for human consumption. The residue, otherwise called as fish paste, is also used for human consumption. The colour of fish sauce varies from straw yellow to amber depending on the species and period of fermentation and its protein content has been found to be varying from 10 to 15%. It is a simple process and involves low capital for its production. Fish sauce, a preferable food item of the people of south East Asian Countries may be used as a condiment in rice dishes and vegetables.

Important fish byproducts


It is high collagen produced from the air bladders (swim bladders) of catfish, carps, eels, polynemids, sciaenids, sea bass, etc. the bladders are first removed from the selected fish and blood and adhering fat materials are scraped off. They are then cut open and washed thoroughly in running water. Then, the outer black membrane is removed by scraping. Subsequently, the bladders are cut into pieces and are dried in an artificial drier or in sun and stored in suitable containers. Isinglass, so prepared is used for clarifying beverages like wine, beer and vinegar. Isinglass also reduces 2 to 0.05% of the suspended solids in beer and increases filtration rate from 3000 to 11,000 liters. It can also be used as an adhesive base and in confectionary product, Indian ink and as an efficient adhesive for glass, pottery and leather. Products with less than 8% moisture content are however, preferred for industrial purposes.


It is prepared by converting the entire trash fish or its offal into animal feed by chemical privations. The product has an advantage over fish meal as the vitamins are not affected in this product which is also free from fish odour. The fresh raw materials are minced and about 10-15 Kg of its placed in a suitable acid resistant container. The meat is acidified first with 3% formaic acid or a mixture of sulphuric acid (50%) and formic acid (85%) in order to maintain a pH of about 3. The container is covered and is left for 3-4 days. The mixture should also be strred daily to bring about quick liquefaction. After liquefaction, oil removal may be necessary if fish with high used.

Pearl Essence

Guanine is deposited in the epidermal layer and on the scales of most of the pelagic fishes. Since those crystalline guanine are suspended in a suitable solvent in the manufacture process, the product is called pearl essence. The scales are collected from pelagic fish as sardines, mackerels, carps, mullets and ribbon fishes and are preserved in 10-15% common salt solution until they are processed. The scales are soaked in gasoline to separate pearl essence from protein and water. The pearl essence is transferred into gasoline where it floats to the surface. The separated pearl essence is then filtered to obtain the fine particles of essence. It is used for photography, ash trays, fishing rods, book covers, textiles, jewellery boxes, umbrella handles and electric light switches.


  1. R. Santhanam (1990), Fishery byproduct, Fisheries Science. Pp145-147.

  2. Ayyappan S. (2006). Fish Processing Technology. Handbook of Fisheries & Aquaculture. Pp.591-633.

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