Fish protein hydrolysates from gold carp (Carassius auratus): I. A study of hydrolysis parameters using response surface methodology

The combined effects of pH, temperature (T), substrate/buffer ratio (S:B) and enzyme concentration (E) on protein recovery from gold carp (Carassius auratus) processing waste with Flavourzyme® were characterised. The effect of hydrolysis parameters on the degree of hydrolysis (DH) was described through response surface analysis (RSA) and the model obtained was defined as follows: DH = −316.30 + 7.1T + 44.5pH + 0.292S:B + 0.27E − 0.048T2 − 2.407pH2 − 0.002S:B2 − 0.307TxpH − 0.002S:BxE. All regression coefficients were significant (α = 0.05). The model showed a good fit with the experimental data, since the R2 of 0.923 indicated that 92.3% of the variability within the range of values studied could be explained by the model. The mathematical model presented a plateau region with a maximum DH (>26.6%) at the following critical values: pH = 5.9, T = 53 °C, S:B = 14.7% and E = 80 LAPU (leucine aminopeptidase units) g−1. Electrophoretic (SDS-PAGE) patterns showed a progressive reduction in molecular weight of the peptidic fractions from 10 min of hydrolysis onwards. By controlling the enzymatic process, it was possible to predict the molecular weight of the peptides obtained, in turn affecting the functional and nutritional properties of the peptidic fractions. Copyright © 2004 Society of Chemical Industry