Regulation of myofibrillar protein gelation by epigallocatechin-3-gallate and carrageenan type: structural and conformational changes associated with gel performance

A concentration-dependent biphasic effect of EGCG on reduced-salt MP gelation was observed. • EGCG-containing MP gels at 0.3 M NaCl were better stabilized by ι-carrageenan. • S–S conformational order was reduced by κ-carrageenan at high EGCG addition. • Raman-derived S–S orderliness was closely associated with gel strength. • EGCG functionality in reduced-salt MP gels was redirected by carrageenan type. Epigallocatechin-3-gallate (EGCG) interacts with muscle proteins, but its concentration-dependent effects on reduced-salt myofibrillar protein (MP) gels and their modulation by carrageenan type remain unclear. This study investigated the effects of κ- and ι-carrageenan on the gelation, cooking loss, molecular structure, and structure–function relationships of MP gels containing 0, 2.5, 5, or 10 μmol/g EGCG. In carrageenan-free MP gels, EGCG exhibited a biphasic effect on gel strength, which peaked at 5 μmol/g (57.13 g mm) but declined at 10 μmol/g (32.61 g mm), accompanied by increased cooking loss (65.84%). Carrageenan type distinctly reshaped this response. Compared with κ-carrageenan, ι-carrageenan showed better compatibility with EGCG-containing MP gels, resulting in lower cooking loss at 10 μmol/g EGCG (59.20% vs. 65.91%) and improved network continuity. Raman and FTIR analyses showed that ι-carrageenan-containing gels exhibited a higher disulfide conformational orderliness index (0.85), together with coordinated amide-region changes including a β-sheet content of 38.8%, whereas κ-carrageenan-containing gels showed lower disulfide orderliness (0.41) and higher cooking loss. Regression analysis identified S–S conformational orderliness as the strongest predictor of gel strength (R 2  = 0.91). These findings indicate that carrageenan does not simply act as a universal gel enhancer in reduced-salt MP systems, but modulates EGCG functionality in a type-dependent manner. This work provides insight into designing reduced-salt meat protein gels using polyphenol–polysaccharide combinations. Carrageenan type directs EGCG modulation of reduced-salt myofibrillar protein gels. Download: Download high-res image (537KB) Download: Download full-size image