Sodium metabisulfite mediated self-assembly behavior of silver carp myofibrillar protein and effects on covalent complexation with (−)-epigallocatechin-3-gallate

Abstract

This study aimed to investigate the influence of different concentrations of sodium metabisulfite on the conformation of the myofibrillar protein (MP) and its covalent complexation with (−)-epigallocatechin-3-gallate (EGCG). Changes in sodium dodecyl SDS‒PAGE and free thiol content indicated that disulfide bonds in MP were disrupted by sodium metabisulfite, resulting in a maximum 3.82-fold increase in free thiol concentration compared to the control group. Fluorescence spectra and circular dichroism analysis revealed that when sodium metabisulfite was added at a concentration of 1 mmol/L, hydrophobic forces drove the self-assembly of MP, leading to a reduction in particle size to 53.21 μm and an increase in β-sheet content to 11.27%. Upon complexation with EGCG, the structure of MP became looser, causing an increase in particle size to 169.01 μm and a significant decrease in α-helix content to a maximum of 39.46%. This study revealed that increasing the concentration of sodium metabisulfite promoted the covalent complexation of MP with EGCG, with the optimal complexation observed at 1 mmol/L sodium metabisulfite, resulting in a notable 97.1% free radical sca0venging activity (compared to 77.8 % in the control group). These findings provide an economical and effective method to alleviate limitations in the food industry regarding MP utilization.