Effects and mechanisms of co-fermentation of sodium sulfite with Bacillus strains on the protein quality of corn gluten meal

Corn gluten meal presents the potential to be a high-quality source of protein in foods. However, poor protein quality limits its application. This study employed sodium sulfite to co-ferment corn gluten-wheat bran mixture (CGW) with keratinase-producing Bacillus strains. The results indicated that fermentation improved the amino acid profile of CGW, concurrently increasing the protein solubility, in vitro digestibility, and in vitro antioxidant activity. Fermentation also resulted in a reduction of the particle size, surface hydrophobicity, protein intermolecular forces, α-helices and random coils in CGW, while increasing the levels of free amino acids free sulfhydryl and β-sheets. Notably, a synergistic effect was observed between sodium sulfite and keratinase during fermentation. Sodium sulfite disrupted the cross-linking of disulfide bonds in CGW, promoting protein unfolding and enhancing the fermentation efficiency. This offers important insights for the development of higher-quality plant-derived proteins in the food industry.