Differences in the post-mortem kinetics of the calpain system in meat from bulls and steers

Abstract

Strip loins (longissimus thoracis et lumborum) from bulls with normal ultimate pH (NOR, pHu < 5.7), bulls with unacceptably high pH (HI, pHu > 5.7), and steers were compared after storage at 15°C. HI samples had higher shear forces 120 hours post-slaughter than NOR and steer samples (P < 0.05). Calpastatin and μ-calpain activities were higher in the NOR bulls than in steers, but the rates of decline in these activities were more rapid in NOR samples. The activity of μ-calpain was low at all times and appeared to be involved in the increased toughness of the HI samples. The activity of m-calpain and the calpastatin : μ-calpain activity ratio provided a good prediction of shear force 120 hours post-slaughter in the strip loin (R2 = 0.70; P < 0.001). This suggests that calpastatin, μ-calpain, and m-calpain all play a role in tenderisation and that on-farm and pre-slaughter management rather than post-slaughter treatment need to be used to decrease the incidence of high pH meat. © 1999 Taylor & Francis Group, LLC.