Antioxidant activities of hydrolysates and peptides generated from high hydrostatic pressure-treated soy protein isolates

Native and pressure-treated (600 MPa) soy protein isolates (SPI) were subjected to in vitro digestion to study the effect of pressure processing on the digestibility of SPI and the antioxidant activity of the hydrolysates and isolated low molecular weight (<1 kDa) peptides. The digestibility of SPI increased significantly (P < 0.05) with pressurization following 10 min of pepsin digestion. The total peptide content in the pepsin-pancreatin hydrolysates was unaffected by pressurization; however, the peptide profiles were altered. Peptides from hydrolysates of pressurized SPI showed higher antioxidant activity than peptides from native SPI hydrolysates as measured by the FRAP assay. In contrast, peptides from native SPI hydrolysates exerted higher antioxidant activity than peptides of hydrolysates of pressurized SPI as assessed by the DPPH assay. These results indicate that peptides from hydrolysates of native and pressurized SPI produce differential in vitro antioxidant activities that might impact their in vivo antioxidative effects