PHYSICO-CHEMICAL AND FUNCTIONAL PROPERTIES OF PROTEINS OF TILAPIA (OREOCHROMIS MOSSAMBICUS)

The properties of total proteins from fresh tilapia (Oreochromis mossambicus) have been assessed. The meat had high moisture (81.34%) and low lipid (< 1%) content. The nitrogen solubility index, with water as solvent, showed minimum solubility of 25.52% of total nitrogen at pH 6.0. The solubility profile of total proteins as a function of molar concentration of sodium chloride indicated maximum solubility at 0.8 M and thereafter it decreased. The total proteins comprised three different fractions as revealed by gel filtration profile. The high molecular weight component was more predominant. The sodium dodecyl sulphate polyacrylamide gel electrophoresis pattern revealed multiple bands in the molecular weight range of 205-18 kDa. Higher value of adenosine triphosphatase (ATPase) activity (4.1 mu g P-i/mg of protein/min) obtained in the present study may be due to combination of sarcoplasmic and myofibrillar ATPase activity. High modori-inducing proteases (MIPase) activity at 55C was observed in the muscle extract that might interfere in the gelling ability. The gel-forming ability of tilapia meat was found to be moderate as indicated by large strain and small strain test. PRACTICAL APPLICATIONS Tilapia is one of the growing aquacultured species all over the world. In India, the mossambique Tilapia (Oreochromis mossambicus) was introduced in inland water bodies like reservoirs to boost the production. Because of its prolific breeding habit and occupation of similar trophic niches, this species has overpopulated many bodies of water. Hence, there is growing need to utilize this species for surimi production and, consequently, generate more revenues for the inland fisheries sector. Knowledge of the physicochemical and functional properties of this species would help in understanding its suitability in surimi production. The rheological properties like dynamic viscoelastic behavior, flow profile, Ca-ATPase activity, and MIPase activity would shed light on the final gel strength of the surimi prepared from this species, and also indicate the guidelines for ameliorating the quality of the gel by addition of different concentrations of cryoprotectants or change of washing cycles.