Preparation and Antioxidant Activities of Walnut Protein Hydrolysates

Many studies have reported that peptides from various food sources possess antioxidant activity. In the present study, walnut proteins were hydrolyzed using Alcalase 2. 4 L to obtain antioxidant peptides. The antioxidant activities of the hydrolysates were measured using 1, 1-diphenyl-2-picryl hydrazyl (DPPH) assay and hydroxyl radical scavenging activity(HRSA) assay. Then, walnut protein hydrolysates were purified sequentially by gel filtration and RP-HPLC. The sequence of the peptide with the highest antioxidative activity was identified to be Ala-Gly-Gly-Ala using RP-HPLC-ESI-MS, which was identified for the first time from walnut protein hydrolysates. The reducing power of the peptide was similar to that of L-glutathione reduced (GSH). These results suggest that the peptide isolated from walnut protein hydrolysates is potent antioxidant and may be effectively used as food additives and as pharmaceutical agents.