槲皮素对氧化条件下猪肉肌原纤维蛋白结构及凝胶特性的影响

为研究槲皮素对氧化条件下猪肉肌原纤维蛋白结构及凝胶特性的影响，建立肌原纤维蛋白氧化体系（40 mg/mL蛋白、10 μmol/L FeCl3、100 μmol/L VC、1 mmol/L H2O2），加入不同量的槲皮素（10、50、100、150 μmol/g），测定蛋白的巯基含量、表面疏水性、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、凝胶强度、保水性、微观结构、流变特性以及水合特性。结果表明，槲皮素使肌原纤维蛋白的总巯基含量显著降低（P＜0.05）；10 μmol/g槲皮素使表面疏水性降低，随后表面疏水性略有增加；槲皮素导致肌球蛋白重链（myosin heavy chain，MHC）条带强度减弱，添加量为100、150 μmol/g时，肌动蛋白条带强度也减弱，MHC和肌动蛋白参与了蛋白质大分子聚集体的形成，并且该聚集体是可被还原的；槲皮素提高了凝胶强度和保水性，凝胶微观结构更加致密，部分自由水转化为不易流动水，蛋白质对水的束缚能力增强，且槲皮素提高了蛋白的G’和G”。因此，槲皮素通过与肌原纤维蛋白巯基的共价交联及适度提高蛋白的表面疏水性，改善了蛋白的凝胶特性，且槲皮素添加量越高，蛋白形成凝胶的能力越强。

Effect of Quercetin on the Structure and Gel Properties of Pork Myofibrillar Protein under Oxidative Conditions

In order to study the effect of quercetin on the structure and gel properties of pork myofibrillar protein under oxidative conditions, an oxidation system (40 mg/mL protein, 10 μmol/L FeCl3, 100 μmol/L VC, and 1 mmol/L H2O2) was established and quercetin at different concentrations (10, 50, 100, 150 μmol/g) was added to the system. Sulfhydryl content, surface hydrophobicity, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) pattern, gel strength, water-holding capacity, microstructure, rheological properties and hydration characteristics were determined after 12 h of incubation in the system. The results showed that quercetin significantly reduced the total sulfhydryl content of myofibrillar protein (P < 0.05). Quercetin at 10 μmol/g decreased the surface hydrophobicity and increased it slightly at higher concentrations. Quercetin weakened the intensity of the band of the myosin heavy chain (MHC) and it also weakened the intensity of the band of actin at concentrations of 100 and 150 μmol/g. Both the MHC and actin participated in the formation of macromolecular protein aggregates and the aggregates could be reduced. Quercetin enhanced the gel strength and water-holding capacity and made the gel microstructure more compact. It resulted in partial conversion of free water into immobile water and enhanced the water-binding capacity as well as the G’ and G” of the protein. Therefore, quercetin improved the gel properties of myofibrillar protein by covalently cross-linking with its sulfhydryl group and properly enhancing its surface hydrophobicity; moreover, quercetin could concentration-dependently enhance the gel-forming capacity of myofibrillar protein.