Thermally driven protein structural reorganization and texture evolution in beef: a multimodal analysis of deep- frying mechanisms

This study systematically investigated the effects of deep- frying temperatures (150 °C, 180 °C, 210 °C) on protein structure reorganization and textural evolution in beef. Through integrating low-field nuclear magnetic resonance (LF-NMR), Fourier transform infrared spectroscopy (FTIR), and biochemical assays, we revealed that elevated temperatures induced hierarchical alterations. Biochemical assays demonstrated progressive increases in protein carbonyl content, lipid oxidation, and protein hydrophobicity, alongside reductions in sulfhydryl content and protein solubility, as temperature increased. LF-NMR analysis indicated a reduction in the proportions of bound and free water, with moisture redistribution into immobilized states at higher temperatures. FTIR analysis revealed temperature-dependent structural transitions: α-helix, β-turn, and β-sheet contents decreased, while random coil content increased, correlating with diminished elasticity and cohesiveness. Additionally, higher temperatures induced surface hardening, limited sodium chloride diffusion and altered color parameters (reduced redness and increased yellowness). These findings underscore the trade-offs between thermal processing benefits and oxidative compromises, providing critical insights for optimizing traditional deep-frying conditions to balance sensory quality, nutritional retention, and consumer acceptability.