** Deputy Director General (Fisheries) Indian Council of Agricultual Research New Deihi, India

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1 PREPARATION AND PROPERTIES OF FUNCTIONAL PROTEIN CONCENTRATE FROM TUNA (Euthynnus affinis) V. MURALEEDHARAN* AND K. GOPAKUMAR** * Central Institute of Fisheries Technology, Cochin, India ** Deputy Director General (Fisheries) Indian Council of Agricultual Research New Deihi, India ABSTRACT A process for the utilization of tuna (Euthynnus affiis) meat in the form of a functional protein concentrate was developed. Mechanically separated mince was washed first with water, then with 2% (wiv) aqueous solution of sodium bicarbonate and finally with water to remove pigments, lipids, colour and odour-bearing compounds. Homogenization of the washed meat in water followed by acidification of the dispersion with acetic acid produced a weak gel which was diluted and spray dried to get a light yellow powder having a faint fishy odour. The spray dried protein powder contained 5% moisture, 1.2% lipid and 89.5% protein and had good functional properties. Packed in 300 gauge polyesterlpolythene laminate pouch, it did not undergo significant browning for 3 months during storage at temperature. INTRODUCTION Tuna is emerging as one of the commercially important Yish species in many developing nations. In India tuna is still an underexploited item. The potential yield of coastal tunas from Indian waters is tons against a catch-of tons (James et al., 1993). Major share of the catch is the little tunny (Euthynnus afjinis) which lacks market demand because of its high black meat content and unappealing taste. The International Workshop on Post harvest Fishery Losses (ICMRD 1988) emphasized the need for developing new products for nutrition enhancement and utilization of resources. In recent years, value addition to tuna and tuna wastes has witnessed significant growth in major markets (Subasinghe, 1996). One of the value-added fish products of global interest is surimi, a washed myofibrillar protein concentrate of fish mince, having characteristic elastic and gelling properties. In the case of dark meat fish, repeated washings with large quantities of water are required to decolorize and deodorize the mince and to remove the sarcoplasmic protein thereby facilitating gelation of the fibrillar protein. Overdilution of wash systems and low freshness of fish make the mince overhydrated and hence unsuitable for surimi (Gopakumar et al., 1992). In such cases the swelled meat can be converted into alternate protein preparations by appropriate technology. The present work reports a method of converting the washed mince of Euthynnus affinis into a free flowing dispersion which is spray dried to a concentrated protein powder. MATERIALS AND METHODS Tuna (Euthynnus aflnis), (length cm) was collected fiom the local fishing harbour immediately on landing. The fish were brought to the laboratory in iced condition. Heading, gutting and filleting were done manually. Mince was prepared using a laboratory model meat bone separator fitted with a d m having 4 mm diameter perforations.

2 Washing Washing of fish mince was done first by cold water, followed by 2% (wlv) sodium bicarbonate solution and finally by cold water. The washing conditions were those described by Muraleedharan et a). (1997) for surimi preparation. Washing was done with a mincelwater ratio 1:3 : In between washings the mince was strained with a close mesh sieve. After the final washing the meat was strained and gently pressed to remove excess water. Preparation of dispersion Washed mince was suspended in 3 times its weight of water. Glacial acetic acid was added dropwise with stirring to a final concentration of 1% (vlw). The suspension was allowed to stand for 2 hrs at room temperature for gelation. Spray drying The dispersion was homogenized using a mixer (Hobart A- 120) and diluted with water to a free flowing consistency. The liquid was then subjected to spray drylng at an inlet temperature of 200 C, and outlet temperature of 1 C. The spray dried fish powder was collected and used for further studies. Proximate composition Moisture, ash, crude protein and lipid were determined according to AOAC (1990) methods. Pepsin digestibility of protein was determined as described by Ambe and Sohonie (1957). Oil Emulsification Capacity The oil emulsifying capacity of the protein powder was determined by the method of Carpenter and Saffle (1964) and was expressed as ml of oil emulsified by 0 mg of protein. Salt solubility Fish powder (lg) was blended with 0 ml water or 1M sodium chloride solution for 1 min. in a Hobart (A-120) blender. Aliquots of 25 ml were centrifuged at 5000 x g for 5 min. Protein was estimated in the supernatant. Density A preweighed ml graduated cylinder was filled with the powder up to ml mark with gentle tapping. The weight of the powder was noted to determine the density. Storage stability The tuna protein concentrate was packed in 300 gauge polyesterlpolythene laminate pouches in the presence of air and was stored at C or at temperature (25-29 C). The samples were observed for changes in colour and odour at monthly intervals. RESULTS AND DISCUSSION Raw tuna had about 40% of its body weight as dark meat. Upon mincing, the dressed fish gave 47% mince yield. The mince was of oily appearance, dark red colour and strong odour. The proximate composition

3 and other characteristics of the raw mince and washed mince are given in Table 1. After the final wash, the meat swelled up because of protein hydration and resulted in a higher level of moisture in the washed mince. The alkali washing removed most of the lipids and blood pigments and greatly improved the appearance: Some of the soluble protein was invariably lost, but it improved the gelation of the fibrillar fraction as reported by Muraleedharan and Gopakumar (1996). Washing with bicarbonate increased the ph of the meat to 9.2 but the final wash with cold water reduced the alkalinity and lowered the ph to 7.1. Exposing the mince to alkalinity, and followed immediately by bringing back to neutrality also seem to have activated the fibritlar protein to improve its gelling ability (Schmidt, 1981). Washed fish proteins formed a weak gel on the addition of acetic acid (ph 3.9). Removal of the lipids and the low molecular weight compounds attached to the structural proteins during washing enhanced the hydrophilic character of the proteins, causing gelation which was further increased with lowering of ph to 3.9 by the addition of acid (Fretheim et al., 1985). This weak gel after proper dilution and homogenisation, formed a free flowing fluid facilitating easy dehydration in the spray dryer. The yield of the powder was 2.5% on whole fish weight. The characteristics of the spray-dried protein concentrate are given in Table 2. Dehydrating the gel in mechanical dryers (4S C, 60% RH) or pacuum dryers produced a coarse powder with brown colour and fishy odour. But dehydration by spray drying produced a light yellow coloured powder of low density and famt fishy odour. Since no solvents are employed for the removal of lipids, the protein in free from the harmful effects of solvent residues. The solubility of the protein m water was about 7.6% but the presence of 1M NaCl enhanced the solubility to about 19%. The high functionality of the powder is also shown by its oil emulsification capacity. The product contains higher protein content (89.5%) compared to the recommended minimum of 75% in type A and 70% in FPC type B defined by FA0 (Halliday and Disney, 1974). The Indlan Standards specify a minimum protein content of 70% on a dry basis and a maximum fat content of 0.75% on a dry basis in FPC (IS ). Total lipid content of the tuna protein concentrate is also lower (1.2%) compared to 5.0% in FPC type B FAO). Storage characteristics The influence of storage conditions on colour and odour of the protein concentrate are given in Table 3. It was observed that the product could remain without any change in colour or dour at C for 3 months. Eiren at conditions these changes were negligible. The polyesterfpolythene laminate having good barrier properties could effectively prevent quality deterioration of the spray dried protein concentrate during the storage period, at both conditions of storage. Table 1. Characteristics and proximate composition of unwashed and washed tuna mince. I 1 Unwashed mince ( Washed mince I Colour Dark red Odour Strong fishy oily Slight fishy Moisture % Lipid % i0.1 Protein % i0.4 Values: Mean2s.d. : (n=5)

4 Table 2. Characteristics of Tuna Protein Concentrate. Yield % (on whole fish weight) Moisture % Protein % Lipid % Ash % Pepsin digestibility % Oil emulsification capacity11 00 mg powder ml Solubility in water % Solubility in 1M NaCl% Colour Odour Density Faint fishy 0.35 Values: Mean3.d. ; (n=5) Table 3. Storage characteristics of Tuna Protein Concentrate Storage Storage temp. in weeks I PC\ Colour Odour Light brown Light brown Brown Faint fishy odour -do- -do- -do- Slight rancid Faint fishy Slight rancid slight rancid Rancid

5 Tuna Heading, Gutting, Filleting Mincing Washing with water 1:3 (wiv) -150C, 15 min Straining Washing with 2% (wiv) sodium bicarbonate solution 1:3(w/v), -15OC, 15 min 4 Straining.1 Washing with water 1:3 (wiv), -15OC, 15 min 3. Sieving, gentle pressing Homogenising in water (l:3 (wlv)) Acidification with acetic acid Gel setting at room temperature Dilution with water, spray drying.1 Spray dried tuna protein concentrate Fig. 1. Flow chart for the preparation of Tuna Protein Concentrate. REFERENCES Ambe, K.S. and Sohonie, K Indian Fish. 4, 1, p.124. AOAC Methods ofanalysis, Association of Official Agricultural Chemists, 15th Ed. Washington D.C. Carpenter, A. and Saffle, R.L Journal Paper 358, College Experiment Station, University of Georgia, Athens, Georgia. Fretheim, K., Egelandsdal, B., Habitz. 0. and Sarnejima, K Food Chem. 18, Gopakumar, K., Muraleedharan, V. and Bhattacharyya, S. K Food Control, 3,2, Halliday, D. and Disney, G Fish protein Concentrate, A review. Tropical Products Institute London. ICMRD Proceedings of the International Workshop on Post Harvest Fish Losses, held on April 12-16, 1987, at the University of Rhode Island, Kingston, RI. Ed. Michael T. Morrissey, Pub. ICMRD, 1988.

6 IS Specifications for Fish Protein Concentrate, Bureau of Indian Standards, New DeIhi. James, P.S.R.B., Gopakumar, G., Mohamed Kasim, Sivadas and Said Koya, K.P Tuna Research in India. (Ed) Sundaresan, D. and John, M.E. Fishery Survey of India, Bombay, Muraleedharan, V. and Gopakumar, K FA0 Fisheries Report.No.563, FIIU/R563, Asia Pacific Fisheries Commission, FAO, Rome, Muraleedharan, V., Antony, K.P., Perigreen, P.A and Gopakumar, K Tropical Science, 37,99-2. Schmidt, R.H Gelation and coagulation. In Protein Functionality in Foorls. P. Cherry (Ed). pp ACS Symposium series 147, American Chemical Society, Washington, D.C. Subasinghe Infofish International, 1,4340.