Abstract
The differences in the proteolytic patterns and shear force of pork and beef during aging were evaluated. Pork and beef semitendinosus muscles were obtained at 24 and 48 h postmortem, respectively, and aged at 4°C for 0 (Day 0), 7 (Day 7), and 14 days (Day 14). Changes in the electrical conductivity were observed in pork on Day 7 and beef on Day 14. The calpain activity increased in pork (p<0.05) after 14 days of aging, whereas that of beef decreased on Day 7 (p<0.05). The cathepsin B activity in pork and beef increased between Day 7 and 14 (p<0.05). The content of α-amino group in the 10% trichloroacetic acid-soluble fraction increased between Day 7 and 14 in pork (p<0.05), but increased steadily in beef throughout aging (p<0.05). The electrophoretogram of the myofibrillar proteins revealed a 30 kDa protein band only in the beef lane on Day 14. The cooked pork had no significant changes in the shear force during aging periods (p>0.05), while the gradual decrease in the shear force with the increasing aging periods was shown in the cooked beef (p<0.05). Circular dichroism analysis of myosin extracts from pork and beef revealed thermal denaturation temperatures of 55°C and 58°C, respectively. This study highlights the different post-mortem proteolytic patterns and thermal denaturation temperatures of myosin in pork and beef semitendinosus muscles, which contribute to distinct changes in the shear force during aging between pork and beef.