Optimization of hydrolysis conditions for the production of protein hydrolysates from fish wastes using response surface methodology

The recycling of waste from food processing is an important industrial procedure for obtaining protein sources with high added value. In this study, trout (Onchorynchus mykiss), anchovy (Engraulis encrasicolus), and whiting (Merlangius merlangus) wastes were hydrolyzed. The hydrolyzation procedure was investigated under the optimum predicted conditions defined by time, temperature, and enzyme ratio (E/S) using alkaline protease (pH 8), Protamex (pH 7), and Flavourzyme (pH 7). The hydrolysis conditions that showed the best degree of hydrolysis (DH%) were optimized using response surface methodology (RSM) with the central composite design (CCD) and Box-Behnken design (BBD) models. The effects of three independent variables, temperature (40–60 оC), time (1–8 h), and enzyme concentrations (1–2%), were examined for model optimization. It was determined that the DH% varies between 50.92% and 74.30% according to the type of fish waste and enzyme. The highest degree of hydrolysis was observed from trout waste (74.30%) and the lowest degree from whiting waste (50.92%) with Flavourenzyme. From this study, it has been shown that different degrees of hydrolysis and protein recovery can be obtained, depending on fish species, waste composition, enzyme type, and hydrolysis method.