OPTIMIZATION OF ENZYMATIC HYDROLYSIS OF SKIPJACK TUNA BY-PRODUCT USING PROTAMEX®: A RESPONSE SURFACE APPROACH

The goal of this study was to optimize enzymatic hydrolysis of the dark flesh of skipj ack tuna (Katsuwonus pelamis). Protamex (R) was used as the hydrolytic enzyme at various concentrations (1%, 1.5%, 2%, 2.5% and 3% w/w) at pHs from 6.5 to 8.5, temperatures from 40 to 60 degrees C and times of 2 to 6 h. The experiment was performed following a five-level second-order central composite design with six replications at the center points. The high coefficients of determination for degree of hydrolysis (R2 = 0.9674) and free tryptophan content (R2 = 0.9426) indicate the suitability of the design for predicting the responses. The optimum hydrolytic conditions predicted by the response surface methodology were 3% Protamex (R) at pH 6.57 and 58 degrees C for 4 h. These conditions resulted in an experimental degree of hydrolysis of 18.48% and free tryptophan content of 72.10 mg kg-1.