Statistical optimization of enzymatic hydrolysis of rice bran protein concentrate for enhanced hydrolysate production by papain

Abstract

Protein hydrolysates having higher degree of hydrolysis (DH) not only exhibit biological activities but also better functionalities than hydrolysates having low DH or intact proteins. The enzymatic hydrolysis of rice bran protein concentrate with papain to obtain protein hydrolysates was optimized using response surface methodology. A central composite rotatable design was used to study the influence of hydrolysis conditions, namely temperature (40–60°C), time (60–180 min), pH (6.0–7.0) and enzyme to substrate ratio (0.02–0.04 w/w) on DH. The experimental values of DH ranged between 14.08 and 33.09%. The second order polynomial model obtained for DH revealed a non-significant value of lack of fit test and coefficient of determination (R2) of 0.96. The optimum conditions for obtaining the higher DH using papain were pH 7.0, temperature 50°C, hydrolysis time 150 min and enzyme to substrate ratio 0.035 (w/w). Under these conditions, the experimental DH of hydrolysate was 34%, which agreed closely with the predicted value (33%). The peptide profile revealed that papain was a potential enzyme to produce protein hydrolysate with more small peptides as compared to free amino acids.