Effects of combined high pressure and enzymatic treatments on physicochemical and antioxidant properties of peanut proteins

Isolated peanut protein (PPI) dispersions were pretreated by high pressure at 100, 300, and 500 MPa prior to enzymatic hydrolysis with alkaline protease (Alcalase). The degree of hydrolysis (DH) was determined by the pH-stat method, the hydrolysates profiles were analyzed by high-performance liquid chromatography (HPLC), the molecular weight distribution (MWD) was analyzed by gel filtration chromatogram (GFC), and content of SH/S-S and antioxidant activity of hydrolysates were evaluated. Results showed that HP pretreatment improved effectively the enzymatic hydrolysis of PPI, with an effective sequence of 300 > 100 > 500 MPa. However, no significant differences were observed in the peak pattern of HPLC profiles, but the peak times were earlier in HPLC profiles of the HP-treated protein. GFC analysis showed that more peptide fractions with low molecular weight appeared in the hydrolysates of the HP-treated PPI with increasing pressure. Moreover, the level of free SH of hydrolysates of the HP-treated PPI was relatively higher than non-HP-treated PPI. The hydrolysates of the HP-treated PPI exerted higher antioxidant activity (reducing power and DPPH radical scavenging) than the hydrolysates of non-HP-treated PPI. The results indicated that high pressure treatment affected the enzymatic hydrolysis of peanut protein and some protein structure properties and improved antioxidant activity of PPI hydrolysates.