Fractionation, Separation, and Identification of Antioxidative Peptides in Potato Protein Hydrolysate that Enhance Oxidative Stability of Soybean Oil Emulsions

The objective of the study was to identify the active peptides responsible for the antioxidant activity of potato protein hydrolysate (PPH). PPH was fractionated using ammonium sulfate precipitation; the efficacy of different fractions for scavenging 2,2 '-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+(.)) radicals and inhibiting lipid oxidation (hexanal, TBARS) in soybean oil-in-water emulsions was investigated. Of all fractions, the fraction precipitated by 50% saturated ammonium sulfate (P50) exhibited the strongest ABTS+(.) scavenging activity and antioxidant activity. Active peptides based on the ABTS+(.) scavenging assay were isolated and purified by RP-HPLC and ultra performance liquid chromatography. Amino acid sequencing by tandem mass spectrometry identified Ser-Ser-Glu-Phe-Thr-Tyr and Ile-Tyr-Leu- Gly-Gln in P50 to be the dominant peptides that matched the sequences in metallocarboxypeptidase inhibitor and lipoxygenase 1, respectively.