Optimizing epigallocatechin gallate-gluten covalent gels through controlled disulfide bond cleavage: Structural...

The spatial architecture of cross-linked protein networks plays a critical role in modulating gel formation and functionality. Given that the functional properties of gluten are highly dependent on disulfide bonds, this study investigated how controlled disulfide bond cleavage regulates the structural and functional characteristics of epigallocatechin gallate (EGCG)-gluten composite gels. Through systematic sodium metabisulfite treatment, we demonstrated that moderate disulfide bond cleavage optimally balances protein unfolding and polyphenol conjugation, resulting in gels with superior mechanical strength and gelling properties. Progressive disulfide bond cleavage induced structural expansion of gluten proteins, exposing hydrophobic domains and enhancing the covalent binding efficiency between gluten and EGCG. This structural modification facilitated the formation of a more homogeneous and robust gel network, thereby improving mechanical integrity. However, excessive cleavage led to over-crosslinking between EGCG and gluten, ultimately disrupting the gel matrix and diminishing its structural stability. Notably, the EGCG-gluten covalent gels exhibited exceptional thermal, pH, and oxidative stability, along with potent antioxidant activity. During simulated gastrointestinal digestion, the gels demonstrated sustained EGCG release, significantly enhancing its bioaccessibility. These findings highlight that precise modulation of disulfide bond cleavage can effectively tailor the physicochemical and digestive properties of protein-polyphenol covalent gels. This strategy offers a promising approach for designing advanced functional food ingredients with enhanced bioactivity and controlled nutrient delivery capabilities, broadening their potential applications in nutraceutical and bioactive delivery systems.