Optimisation of hydrolysis conditions for antioxidant hydrolysate production from whey protein isolates using response surface methodology

The hydrolysates of whey protein isolates (WPI) by papain were found to possess antioxidant activity. Response surface methodology (RSM) was used to improve the antioxidant activity of these hydrolysates. The model was validated and shown to be statistically adequate and accurate in predicting the response. For both 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical-scavenging activity and reducing power responses, the optimised conditions were achieved at an enzyme to substrate ratio (E/S, w/w) of 2.22%, hydrolysis time of 3.60 h, and hydrolysis temperature of 45.70 °C. Under the optimised conditions, DPPH radical-scavenging activity of the hydrolysates of WPI was 31.48% and the reducing power was 0.612 at 700 nm. The results of confirmation experiments indicated that the model was powerful and suitable for estimation of the experimental value. The hydrolysate of WPI has potential application as an antioxidant in food products.