Enzymatic hydrolysis of Nile tilapia (Oreochromus niloticus) myofibrillar proteins: effects on nutritional and hydrophilic properties

Protein concentrate (PC) was prepared from eviscerated and mechanically deboned fish. The pulp was washed sequentially with 0.05 M NaCl and 4 g l−1 NaHCO3 solutions, with cold ethanol and then with hot (50 °C) ethanol. Subsequently, it was dried (40 °C) and ground to 60 mesh. Enzyme (Flavourzime®) hydrolysates were prepared with a degree of hydrolysis (DH) ranging from 3.5 to 45%. The PC was characterized for proximate composition, amino acid profile, physical and functional properties. The influence of DH on functional and nutritional properties was evaluated. Hygroscopicity increased in all hydrolysates for environmental relative humidities above 40% and solubility increased rapidly for DH above 7%. Water retention, water absorption and oil absorption all decreased as a function of DH. The pH (3 to 9) influenced the water and oil absorption of the hydrolysate with 7% DH. A pH near the isoelectric point tends to decrease water absorption but increase oil absorption capacity. The insoluble fraction (IF) of the hydrolysates presented a better amino acid profile than the soluble fraction (SF). The nutritional indexes determined for the IF did not differ from the total hydrolysate, but they were consistently higher than those for the SF.