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Research and development work on fish-enriched protein foods from inexpensive varieties of fish

M.N. Moorjani
Meat, Fish, and Poultry Technology Division, Central Food Technological Research Institute, Mysore, India

Malnutrition among the poor in many countries is widespread. Protein calorie malnutrition has been an important cause of infant and child mortality in developing countries, and consequently major emphasis has been placed on the processing and utilization of protein-rich foods. Among the several foods available for protein enrichment, fish offers a good potential to meet this demand because it is one of the cheapest sources of protein.

The total catch of fish in India currently is around 2.4 million tons, but possibilities exist to increase it considerably using improved methods. A fair percentage of these fish are small, bony, and devoid of good taste (table 1). The present paper relates to studies on the use of inexpensive varieties of fish for the production of fish-enriched protein foods.

TABLE 1. Estimated Catches of Some Inexpensive Varieties of Fish in India, 1979

PROCESSED FISH PRODUCTS

Odourless Fish Protein Concentrate

Dressed fish, after cooking and pressing in a basket press, is extracted with absolute ethanol. The solvent dehydrates, defats, and deodorizes the muscle tissue (1). After extraction, the material is vacuum-dried, powdered, and packed in suitable containers such as round cardboard boxes. The solvent, after treatment with dilute H₂SO₄, is distilled, rectified, and dehydrated for re-use (fig. 1). The final product contains around 80 per cent protein and traces of fat. The product is free from pathogenic organisms, bland tasting, and not gritty, and flavour reversion does not occur (1). Its available Iysine content is 9.96 g/100 g protein.

Biological evaluation of this fish protein concentrate (FPC) by feeding it to severely protein-depleted young albino rats showed that it is of high protein quality and free from toxic products. FPC was found to be useful in treating patients with kwashiorkor and other forms of protein-calorie malnutrition because it is readily available, keeps well, and is non-toxic.

FPC was given to six- to twelve-year-old children in the form of protein chapaties (a flat, baked, unleavened bread) made from wheat and low-fat peanut flour, Bengal gram (Cicer arietinum) flour, and FPC in a ratio of 2:1:1. Daily, each child in the experimental group of 29 boys from low-income homes was given 40 9 of this high-protein food containing 20 9 of protein. The caloric intake of a control group of 29 boys was adjusted to equal that of the experimental group. All the children in the experimental group relished this protein food. After six months, a highly significant increase was observed in height, weight, red blood cell count, and haemoglobin level of the subjects receiving the protein food supplement compared with the control group (2).

FIG 1. Simplified Flow-sheet of FPC Processing.

(1) Chopper, (2) cooker, (3) press, (4) extractor, (5) drier, (6) hammer mill, (7) receiver for condensed solvent, (8) receiver for miscella, (9) distillation unit, (10) fractionating and dehydration columns, (11) vacuum pump

FPC could easily be incorporated at a 10 per cent level in a number of food preparations. In bread and biscuits, a 2.5 per cent level (depending upon the varieties of fish used) is optimum. Higher levels result in poor colour, crumb quality, and loaf volume, although FPC made from white-muscled fish can be added at a slightly higher level.

Partially Deodorized and Defatted Fish

Some people enjoy the flavour and texture of fish, and for them products in which the fish flavour is retained might well be competitive with more highly processed FPC. As most fish lipids carry unsaturated fatty acids that are highly prone to oxidative reactions and the interaction between proteins and these oxidized lipids causes a considerable decrease in the nutritional value of the fish and associated changes in colour and flavour, however, it is necessary that the lipids should be stabilized against oxidation.

Soluble Fish Proteins

Deodorized FPC does not dissolve in water. However, proteins of fish treated with ammonia (4) show an improvement in this functional attribute (5). Under optimum conditions of processing, the proteins are solubilized, fat is released, and the bones and connective tissue can be separated out. Such soluble proteins have practical possibilities as a base material for beverage-like preparations with a malt or other acceptable flavour.

FISH-ENRICHED FARINACEOUS PRODUCTS

Fish Wafers

Cassava or tapioca (Manihot utilissima) is grown in large quantities in various parts of the world. The tuber contains a negligible amount of protein, but its starch has certain unique properties that are conducive to globule formation.

An attempt has been made to enrich the starch from cassava with high-quality proteins from inexpensive varieties of fish (6). The tubers deteriorate and discolour rapidly through oxidation of the leucoanthocynins that are mainly located in the inner layer of the cortex, and so they should be procured fresh and used within 24 hours. They are washed with water and hand-peeled. The peeled tubers are mechanically grated and blended in a Waring blender with three times the quantity of water. The blended material is strained through a linen cloth (mesh about 50), through which starch and water pass leaving a residual portion on the cloth. This starchy slurry is then allowed to settle for two to three hours. When completely settled, the starch is in the form of a thick paste and the supernatant liquid is siphoned off. At this stage the starch contains about 50 per cent moisture, and it can be used as is or after drying. About 20 kg of starch and 10 kg of residue are obtained from every 100 kg of tubers.

The meat from eviscerated fish is separated using a machine fitted with a wide, flexible rubber belt and a perforated stainless steel drum. As the fish pass between the rubber belt and drum, the meat, being soft, is separated in the drum by the squeezing and tearing action of the machine. The softer, less cohesive muscle is forced through the perforations of the drum; skin and bones remain behind on the belt.

Cassava starch in wet form (moisture 50 per cent) is mixed with separated meat in a ratio of 1:1, with salt added to taste. The blend is broken down into small pieces by passing it through an 8 mesh stainless steel sieve and then granulated into a globule form using a reciprocating-type mechanical shaker (see photo). These globules are passed through 2-mm-hole sieves to obtain uniform-sized globules. The globules, after partial gelatinization, are arranged in single, compact circular layers 2 inches in diameter in a mould block, sprayed with a fine mist of water, and steamed to gelatinize the starch content. This process firmly binds the globules to each other. The gelatinous material is then dried in a through-flow drier to a moisture content of 5 to 6 per cent at 45° to 50° C.

After drying, the wafers become detached from the mould and are packed in polythene bags. These wafers can be fried in an edible fat for a few seconds until they expand and become very crisp, and can thus be used as a snack.

Use of Shrimp in Wafers

Only a small percentage of shrimp muscle can be incorporated into the mixture because it affects the granulation property. If a higher percentage is to be used, the minced muscle should be treated with 0.2 per cent papain or bromelin for about an hour at 50 C (pH 5.5) to partially break down the proteins. The muscle is then strained through a mull cloth to separate the connective tissues and any larger muscle pieces. This paste is blended with cassava starch to produce wafers with a shrimp flavour and a protein content of about 20 per cent.

Fricola

To make fricola (3), minced fish muscle is cooked and blended with cooked rice in a ratio of 3:1 with a suitable quantity of shredded coconut (4 per cent on dry basis of the product). The blend, after flavouring with vanilla, is dried in the form of thin flakes on a stainless steel roller drier at about 30 psi steam pressure. Any pieces of bone in the dried product are removed by passing it through 8 and 16 mesh sieves. The product has an attractive white colour and is almost free of fish smell. It has a 35 per cent protein content, and available Iysine content is of the order of 9 per cent of total protein. It is effective in treatment of mild cases of kwashiorkor (table 2) (7).

TABLE 2. Results in Children with Mild Kwashiorkor Treated with Fricola

Fricola protein fed at 5 g/kg body weight/day.

The consumer adds liquid in the form of water or milk to yield a porridge-like product on heating. Children enjoy it after sugar is added. It can also be used for savoury preparations like curd (a yogurt-type product) by adding lime juice, salt, and other condiments.

Because fricola in flake form is very light, it has been compressed into briquettes, each weighing about 25 9, to overcome packaging problems.

Fish Noodles

Cassava starch blended with fish muscle and semolina containing Tenox II (0.01 per cent BHA + 0.003 propyl gallate + 0.005 per cent citric acid) is extruded through a vermicelli press in the form of a hollow tube. The resulting noodles are dried in a current of hot air. The finished product is cheap and highly nutritious, containing 20 per cent protein of high biological value. A measured quantity of the vermicelli is dropped into six times its quantity of vigrously boiling water. The product cooks in about ten minutes, depending upon the degree of softness desired; loss of solids into the cooking water is negligible. After draining, the cooked vermicelli is ready to serve with any savoury household preparation.

SUMMARY

This review describes efforts to produce different types of fish protein concentrates from inexpensive varieties of fish. While deodorized and defatted fish protein concentrates have a specific role to play, there are other possibilities for low-cost fish products such as fricola (35 per cent protein), fish noodles, fish wafers (20 per cent protein), and instant soluble fish (80 per cent protein), wherein the fat is partially removed and the product is also stabilized, which may have greater consumer appeal.

An extensive study sponsored by the US Agency for International Development showed that nearly 36 per cent of the world population is protein-deficient. Because all age groups are likely to require an increased availability of high-quality proteins to supplement vegetable proteins that are generally deficient in Iysine, methionine, and tryptophan, fish protein concentrates have a good potential for meeting this demand.

REFERENCES

1. M.N. Moorjani, R.B. Nair, and N.L. Lahiry, "Quality of Fish Protein Concentrates Prepared by Direct Extraction with Various Solvents,', Food Technol., 22:1557 (1968).

2. T.R. Doraiswamy, S.R. Shurpalekar, M.N. Moorjani, N.L. Lahiry, A.N. Shankaran, M. Swaminathan, A. Sreenivasan, and V. Subrahmanyan, "Fish Protein Food in Feeding Trials with School Children,", Indian J. Pediat, 30: 266 (1963).

3. M.N. Moorjani, A.N. Upadhye, N.L. Lahiry, and H.A.B. Parpia, ``Fricola: A Fish-Enriched Farinaceous Product,,, paper presented to FAO symposium, 26-30 May 1964, Husum, FRG.

4. V. Subrahmanyan, N , L. Lahiry, M.N . Moorjani, R.B. Nair, and M.A, Krishnaswamy, "Ammonia- Possible use for Preserving Fish,"Science, 142:233 (1963).

5. M.N, Moorjani, "Soluble Fish Proteins,,' paper presented to a symposium on the Fish Processing Industry in India, CFTRI, Mysore, 13-14 Feb. 1975.

6. M.N. Moorjani, "Processing of Protein-Enriched Wafers," Food Technol., 24: 60 (1970).

7. S.M. Pereira, T. Isaca, B.. Tewarson, and M.E. Dumm, `'Processed Fish Protein (Fricola) in the Treatment of Kwashiorkor," Indian J. Med. Res., 53:651 (1965).

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