Dual Role (Anti- and Pro-oxidant) of Gallic Acid in Mediating Myofibrillar Protein Gelation and Gel in Vitro Digestion

The dose-dependent effects of gallic acid (GA; at 0, 6, 30, and 150 mu mol/g protein) on chemical changes and gelling properties of oxidatively stressed porcine myofibrillar protein (MP) and in vitro digestibility of the gels were investigated. The incorporation of GA suppressed lipid oxidation and protein carbonyl formation but promoted the loss of thiol and amine groups, destabilization of the tertiary structure, aggregation, and cross-linking. The gelling potential (storage modulus) of MP was increased by nearly 50% with 6 and 30 mu mol/g of GA, corresponding to enhanced protein unfolding and aggregation and formation of disulfide-dominant covalent bonds. However, GA at 150 mu mol/g induced macroscopic aggregations and insolubility of MP, resulting in poorly structured gels. Despite the oxidative changes, MP gels did not show reduced susceptibility to digestive enzymes in vitro.