Abstract:

Objective: To compare the difference in shear force, intramuscular fat content, μ-calpain and protein degradation
between Meishan and crossbred pigs in order to explore the factors contributing to the tenderness of Meishan pork. Methods:
Six purebred Meishan pigs and six crossbred pigs (Duroc × Landrace × Yorkshire) were slaughtered. μ-Calpain at 45 min
postmortem, integrin and nebulin degradation at 1, 3 and 7 d of postmortem aging were determined by polyacrylamide gel
electrophoresis (PAGE) and western blotting. Results: Meishan pork presented lower shear force and higher intramuscular
fat content compared to crossbred pork (P < 0.05). At 45 min postmortem, crossbred pork presented enhanced degradation of
μ-calpain, as evidenced by significantly lower proportions of 80 kD fragments and significantly higher proportions of 78 kD
and 76 kD fragments percentage compared to Meishan pork (P < 0.05). Lessened degradation of μ-calpain in Meishan pork
at 45 min postmortem potentially forecasted that Meishan pork could have lower protein degradation during the subsequent
aging time. The degree of integrin degradation was lower in Meishan pork compared to crossbred pork at 3 and 7 d of
postmortem aging. Additionally, the relative optical density of nebulin was lower in Meishan pork compared to crossbred
pork at 1 and 3 d of postmortem aging, which represents lower degradation of nebulin. Conclusion: μ-calpain and protein
degradation may not be key factors contributing to the higher tenderness of Meishan pork, while the higher intramuscular fat
content may help explain the lower shear force in Meishan pork.

Key words: Meishan pig, μ-calpain, integrin, nebulin