Abstract:

The optimal processing conditions and antioxidant activity of soybean peptides prepared by Aspergillus niger fermentation were investigated and the molecular weights of soybean peptides were determined. The highest concentration of soybean peptides in the fermentation broth, 3.38 mg/mL, was achieved under the optimal preparation conditions, which were the inoculation amount of 2%, fermentation pH of 6.0, substrate concentration of 9 g/100 mL and fermentation time of 34 h. Fractions I and II were obtained from the fermentation supernatant of soybean meal through Sephadex G-15 gel permeation chromatographic separation. Both of them exhibited DPPH and hydroxyl free radical scavenging activities and inhibitory effect on lipid peroxidation, which were all linearly dependent on concentration, and fraction I was superior to fraction II. Moreover, it was found that the molecular weights of fractions I and II were 675.58D and 1625.54 D, respectively.

Key words: soybean peptide, Aspergillus niger, fermentation, antioxidation