Differential modulation of myofibrillar protein gelation by monophenolic acids with divergent sidechain groups

Six phenolic acids (PAs) with related structures, i.e., gallic acid (GA), syringic acid (SA), coumaric acid (CMA), caffeic acid (CFA), ferulic acid (FA), and chlorogenic acid (CA), were compared for their effects on the gelling properties of myofibrillar protein (MP) under oxidative conditions. Of the six PAs, only the smallest GA caused significant reductions of free amine and sulfhydryl content (by 26% and 7%, respectively, P < 0.05) and SA decreased protein carbonyl formation, while CA, the largest PA with an esterified quinic group, prevented oxidative loss of amines. All PAs quenched MP fluorescence with CA showing the highest efficacy (38% suppression). During thermal gelation, the GA-modified MP displayed the strongest myosin cross-linking. The elasticity (G′) and breaking strength of MP gels were markedly enhanced by the addition of PAs, and the final G′ value ranked in the order GA > CA > FA > CMA > SA > CFA, indicating complex roles of phenolic side groups.