Optimization of enzymatic hydrolysis of skipjack tuna by-product using protamex ®: a response surface approach

Abstract

The goal of this study was to optimize enzymatic hydrolysis of the dark flesh of skipjack tuna (Katsuwonus pelamis). Protamex® 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 oC 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 centeer 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® at pH 6.57 and 58 °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.Keywords: Skipjack tuna; protein hydrolystate; response surface analysis; free trytophan