Abstract: Myofibrillar proteins from Bama ham, Jinhua ham, Xuanwei ham and Parma ham as typical representatives of dry-cured hams were compared for surface hydrophobicity, sulfhydryl and disulfide bond contents, ultrastructure, particle size and in vitro digestibility. The results showed that the surface hydrophobicity of myofibrillar proteins in Jinhua ham was significantly higher than that of the other hams (P < 0.05). Ultrastructure analysis showed that myofibrillar proteins in Jinhua ham had the lowest degree of cross-linking or aggregation along with a more stretched conformation, while myofibrillar proteins in Parma ham had the largest degree of aggregation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that myofibrillar proteins in Jinhua ham were significantly degraded during in vitro digestion, resulting in a decrease in the particle size. The highest proteolysis rate of myofibrillar proteins was observed in Jinhua ham, while the lowest proteolysis rate was presented in Parma ham after pepsin, trypsin and α-chymotrypsin incubation among the four hams (P < 0.05). This study indicated that the exposure of hydrophobic groups and protein unfolding could provide more recognition sites for digestive enzymes, accelerating the hydrolysis of myofibrillar proteins in Jinhua ham. It demonstrated that the degree of oxidation of myofibrillar proteins significantly affected their digestibility.

Key words: dry-cured ham, myofibrillar proteins, protein structure, in vitro digestion, proteolysis rate