Effects of rice vinegar treatment on the antioxidant activities and protein structures of whole egg liquid before and after gastrointestinal digestion

Abstract

In this study, the effects of vinegar treatment on the antioxidant and structural properties of whole egg proteins were investigated. The results showed that the degrees of hydrolysis (DH) of vinegar-treated egg liquid (VE) and digested VE (DVE) increased after vinegar addition. A similar trend was also found for the antioxidant activity of DVE but not for that of VE. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results showed that vinegar treatment increased the gastrointestinal hydrolysis of whole egg protein compared with that of digested egg liquid (DEL) protein, which was in agreement with the free amino acid content results. The Fourier transform infrared (FTIR) analysis results indicated that proteins from VE_1:3 tended to form β-sheet structures, whereas proteins from DVE_1:3 accumulated α-helices and turns. Vinegar treatment has great potential as a nonthermal processing method for promoting gastrointestinal digestion and producing superior antioxidant peptides.

Keywords: Antioxidant activity; Egg protein; In vitro digestion; Nonthermal processing; Vinegar.