Influence of RosA-protein adducts formation on myofibrillar protein gelation properties under oxidative stress

The effects of different concentrations (0, 0.05, 0.25, and 1.25 mM) of rosmarinic acid (RosA) on the gelling characterization of porcine myofibrillar protein (MP) were evaluated. Supplementation of RosA significantly decreased the contents of a-helix and alpha-sheet, while increased the contents of beta-turn and random coil. The rheological and gelation properties with0.05 and 0.25 mM RosA-treated samples were improved, while 1.25 mM RosA was detrimental to MP gelation. Three hydrolytic adducts were identified by UPLC-quadrupole time-of-flight mass spectroscopy including 3,4-dihydroxy,5-N-6-argininocinnamic acid, 3,4-dihydroxy,5-N-4-histidinocinnamic acid and 3-(3,4-dihydroxyphenyl,5-cystein-S-yl. In the presence of low concentrations of RosA (0.05, 0.25 mM), both RosA-Cys and Arg/His-RosA-Cys adducts formed, which exerted positive effects on the protein gelation properties. With high concentration of RosA (1.25 mM), RosA-Cys became the dominant adduct and blocked the thiol groups on MP from forming disulfide cross-link, which reduced water holding capacity and weakened gel strength by undermining protein gelation. (C) 2017 Elsevier Ltd. All rights reserved.