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

Abstract: 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.