Abstract: Waste silk was used as raw material in this study.Fibroin peptide were prepared by degummed and hydrolyzed of Alcalase2.4L.In addition,superoxide anion free radical (O₂^·-),hydroxyl free radical (·OH) and DPPH free radical (DPPH·) assays were used to evaluate free radical scavenging activities of fibroin peptides.The results showed that fibroin peptides with DH value 0-23.92% can be obtained by controlling the reaction time under the following conditions:substrate concentration of 5%,enzyme dosage (［E］/［S］) of 2%,temperature of 60 ℃,pH 8.5.As the hydrolysis degree increased,scavenging rate of silk fibroin peptide was continuously enhanced in the range of DH.The silk fibroin had the highest antioxidant activity when the DH was 23.92%.The scavenging rates of silk fibroin peptide with DH 23.92% on O₂^·-,·OH and DPPH· were 73.69%,82.49% and 70.79%,respectively.

Key words: silk protein, silk fibroin peptide, antioxidant activity, enzymatic hydrolysis