Structure and emulsifying properties of rice bran protein alkylated using an electrochemical reactor

Abstract

To replace the application of reducing agents for protein alkylation, electrochemical reduction techniques have been considered. In this study, a custom-made electrochemical reactor was used to alkylate rice bran protein (RBP). The structure, morphology, and emulsification properties of RBP were investigated under different voltages. When treated at 35 V, the content of the α-helix and β-sheet of RBP decreased at first and then increased, whereas the content of the β-turn and random coil increased steadily. The CH₃ group of RBP was exposed and S-S decreased. The endogenous fluorescence spectral curve exhibited a redshift. The free sulfhydryl (-SH) content increased. The average particle size of the modified RBP decreased by 69.35 %, and its zeta potential decreased to -21.8 mV. Atomic force microscopy (AFM) revealed that the treated protein particles dispersed more evenly and their roughness (Rq) decreased. The contact angle, water holding capacity (WHC), fat holding capacity (FHC), and solubility were enhanced. The emulsification capacity increased to 65.82 m²/g and emulsification stability increased to 36.34 min. These results demonstrated that the RBP was alkylated by the electrochemical reactor and the modified RBP showed improved emulsification properties compared to the untreated RBP.

Keywords: Alkylation; Electrochemical reactor; Emulsifying properties; Rice bran protein; Voltage.