Advantages of an acid protease from Aspergillus oryzae over commercial preparations for production of whey protein hydrolysates with antioxidant activities

Whey protein is a byproduct of the dairy industry that has high nutritional, functional and biological value. Enzymatic hydrolysis, which is a novel application of whey protein that is used to generate bioactive peptides with antioxidant properties, has attracted a great deal of attention. The aim of this study was to evaluate the effects of the enzymatic hydrolysis of bovine whey protein on its antioxidant properties. The parameters of hydrolysis, including protease and substrate concentrations, hydrolysis time and the partitioning effects of the hydrolysates by ultrafiltration, were further investigated. The hydrolysates were prepared with a protease from Aspergillus oryzae LBA 01 (AO) that was produced by solid-state fermentation and two commercial proteases, a protease from A. oryzae (CAO) and a protease from Bacillus licheniformis (CBL). The results of this study demonstrate the viability of using the protease from A. oryzae LBA 01 (AO) to increase the antioxidant capacity of whey protein compared to two commercial protease preparations. The hydrolysis parameters defined according to the experimental design were: substrate concentration of 8.0% and addition of 70.0 U of protease per mL of reaction, resulting in 424.32 and 16.39 Trolox EQ μmol g−1 for the ORAC and DPPH assays, respectively. The maximum antioxidant activities were observed from 60 to 240 min of hydrolysis, where the degree of hydrolysis and residual protease activity were approximately 44.0 and 50.0%, respectively. The highest antioxidant activities were detected in fractions obtained by ultrafiltration with molecular weights below 3 kDa.