Study on the effects of representative spice polyphenols on the in vitro digestive properties of tilapia myofibrillar protein and its mechanism of action: based on physical and chemical properties and enzyme activity

Abstract

Food flavorings are essential components in processing due to their safety, efficacy, and additional flavour and nutritional benefits. To investigate the effects of polyphenolic compounds in flavorings on protein digestibility, this study selected five high-concentration phenolic compounds (quercetin, 8-gingerol, naringin, apigenin, and ferulic acid) from flavorings to prepare protein-polyphenol complexes. Simulated gastrointestinal digestion results showed that protein digestibility was significantly reduced after polyphenol binding; SEM and AFM revealed that protein structure was disrupted by polyphenol addition; FT-IR confirmed changes in secondary structure, particularly a reduction in α-helix content. Fluorescence spectroscopy, molecular docking, and molecular dynamics results indicated that polyphenols bind to proteins via non-covalent bonds, exhibiting quenching effects on fluorescent amino acid residues in proteins; two-dimensional and three-dimensional spectroscopy and molecular docking confirmed that the five phenolic compounds bind to digestive enzymes via hydrogen bonds and hydrophobic interactions, causing static fluorescence quenching of digestive enzymes and reducing their digestive activity. This study provides insights into the interaction mechanisms between plant-derived polyphenols, tilapia protein, and proteases at the physicochemical and enzymatic activity levels, which may help expand the application of tilapia protein-polyphenol complexes in the food industry and provide a basis for the development and optimization of tilapia processed foods.