Optimization of enzymatic hydrolysis of yellowfin tuna Thunnus albacares viscera using Neutrase

Enzymatic hydrolysis of yellowfin tuna visceral protein using Neutrase was studied by response surface methodology using factorial design. Degree of hydrolysis (DH; %) has been estimated as a response surface to the hydrolysis conditions (enzyme activity, reaction temperature, and reaction time). R2 of 0.91 for the mathematical model indicated that 91% of the variability within the range of values studied could be explained by the model. Lack-of-fit test revealed a non-significant value for the model, indicating that the regression equation was adequate for predicting the degree of hydrolysis under any combination of the variables (P < 0.05). Enzyme activity of 39.61 AU/kg protein, temperature of 53° C, and hydrolysis time of 141min were found to be the optimal conditions to reach 30% degree of hydrolysis. The tuna visceral protein hydrolysates had relatively high protein (74.56%), and low lipid (1.86%) content. The chemical score of the hydrolysate indicated that it fulfils adult human nutritional requirements except methionine. Lysine and methionine were the first and the second limiting amino acid in that order. Phenylalanine was predominant amino acid in the hydrolysates with respect to common carp requirement.