Covalent interactions between rabbit myofibrillar proteins and quercetin: A promising approach to enhance protein antioxidant capacity and thermal stability

Abstract

Meat-derived protein is suitable for converting into medical fluid food because of its high nutritional value, but industrial heat-treatment is easy to lead to fluid protein aggregation and sedimentation. The pH-shift method was utilized for production of rabbit myofibrillar proteins (MPs)-quercetin conjugates to enhance MPs thermal stability. The MPs-quercetin conjugates showed improved in water solubility compared to free quercetin (from 3.64 μg/mL to 54.83 μg/mL at 100 μmol/g protein), thus elevating the antioxidant capacity. The conjugates simultaneously imparted MPs to better thermal stability, as the quercetin concentration increased, the solubility of heat-treated MPs increased from 18.34% to 80.53% while high quercetin concentration (100 μmol/g protein) caused a decrease in solubility (68.33%, p < 0.05) due to excessive cross-linking of the myosin head and tail. Nano LC-ESI-MS/MS confirmed the amino acids conjugated with quercetin mainly included lysine and arginine, but less conjugated with sulfur-containing amino acids. Enhanced thermal stability was related to the steric hindrance provided by MPs-quercetin aggregates with different molecular weights. Quercetin could also mask the hydrophobic groups on the surface of MPs and enhance the hydrophilicity of protein, thus contribute critically to the dispersion stability after heating.