Abstract: In the present study, the preparation of antioxidant peptides derived from Ginkgo biloba kernel by stepwise enzymatic hydrolysis with alkaline protease 2709 and pepsin was optimized. Four process conditions affecting total reducing power activity of antioxidant peptides including enzyme dosage, temperature, pH and hydrolysis time were investigated. Using response surface methodology, the optimal conditions for hydrolysis of alkaline protease 2709 were determined as follows: 6976 U/g enzyme dosage, 55 ℃ hydrolysis temperature, pH 8.9 and 5 h hydrolysis time, and the total reducing power activity (expressed as absorbance at 700 nm, A700 nm) of the resulting hydrolysate was 1.278. For the subsequent pepsin hydrolysis, the optimal hydrolysis conditions were determined using orthogonal array design to be: 9000 U/g enzyme dosage, pH 3.0, 50 ℃ hydrolysis temperature and 2 h hydrolysis time, and the resulting reducing power A700 nm was 1.636.

Key words: Ginkgo biloba, alkaline protease 2709, pepsin, enzymatic hydrolysis, antioxidant peptide