Abstract: Our previously reported work has shown that one-step enzymatic hydrolysis with neutral and alkaline proteases allows the preparation of highly antioxidant goat,s milk casein hydrolysates. In this study, hydrolysis conditions for the preparation of goat,s milk casein hydrolysates by the method were optimized using uniform design based on radical scavenging activities against hydroxyl and DPPH free radicals. The results showed that hydrolysis for 24 h at 45 ℃, pH 7.5 and 60 g/kg substrate concentration with 4000 U/g neutral protease and 250 U/g alkaline protease proved optimal. The EC50 concentrations of the obtained hydrolysate for scavenging hydroxyl and ABTS+ · and chelating Fe2+ were 3.59, 158.72 times and 5.44 times higher than those of goat,s s milk casein, respectively. Moreover, this hydrolysate revealed stronger inhibitory effect on lipid peroxidation in linoleic acid model system and was equivalent to VE. The scavenging activities against hydroxyl, DPPH, superoxide anion and ABTS+ could not replace each other.

Key words: goat,s milk casein hydrolysates, preparation, antioxidant activity, EC50