In vitro protein digestion of pork cuts differ with muscle type.

Porcine trapezius, longissimus dorsi and biceps femoris muscles have been shown to contain different types of muscle fibers. Little is known about the differences in digestibility among cooked pork cuts. In this study, we compared the protein losses of porcine trapezius, longissimus dorsi and biceps femoris muscles under in vitro digestion conditions. Meat samples were cooked in 72°C water bath to center temperature of 70°C. Then meat samples were homogenized and incubated with pepsin alone or followed by trypsin. The in vitro protein losses and particle size were measured. The pepsin and trypsin digestion products were separated and identified by SDS-PAGE and Nano LC-LTQ-Orbitrap XL MS/MS. The results indicated that longissimus dorsi muscle had the highest losses under both pepsin and trypsin treatments (P<0.05). In untreated samples, biceps femoris muscle showed the greatest particle size (P<0.05), but enzymatic treatment decreased particles to the similar size for all the three muscles (P>0.05). Proteome analysis indicated that biceps femoris muscle had the highest susceptibility to digestion. Interaction analysis reveals that differential proteins mainly are related to glycolysis and muscle contraction. And thus fiber types could be the key factor to cause the differences in protein composition and their susceptibility to digestion.