Abstract
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.
Highlights
The industrial process of high pressure (HP) is a potential processing technique and used as an alternative to heat treatment in food industry (Chawla, Patil, & Singh, 2011)
The degree of hydrolysis (DH) of HP‐treated PPI was near or lower than that of non‐HP‐treated PPI within the first 180 min except the treatment at 300 MPa, which confirmed that peanut protein after high pressure treatment was not easy to be degraded efficiently by Alcalase
The DH of the HP‐treated PPI increased gradually with extending hydrolysis time and became higher than non‐HP‐treated PPI after 180 min of hydrolysis, which may be related to high pressure causing aggregation of some structures of proteins
Summary
The industrial process of high pressure (HP) is a potential processing technique and used as an alternative to heat treatment in food industry (Chawla, Patil, & Singh, 2011). Recent research confirmed that high pressure had an active impact on protein hydrolysis by increasing the proteolysis degree Préstamo, and Gomez (2004) found that high pressure treatment of 100 MPa contributed to the hydrolysis of soy whey protein treated by different proteases. Belloque, Chicón, and López‐Fandiño (2007) reported that HP treatment at 200 MPa changed the structure, elasticity, and flexibility of proteins, which was related to the protease specificity and hydrophobic groups or aromatic groups embedded in the center of the original protein. The original structure of protein without HP treatment was difficult to be hydrolyzed by protease (Belloque et al, 2007; Chicón, Belloque, Alonso, & López‐Fandiño, 2008)
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