| In recent years, the requests of people on edible quality of livestock and poultry meat are improved. Of lots of quality indicators, tenderness is the most important; Consumers are willing to buy well-tenderness meat with higher price. The present study suggests that the changes of muscle tenderness after slaughter are affected by the synergy of a variety of enzymes, one of the important part is the hydrolysis of calpains on bone cell and the myofibril protein. Calpains system consist of μ-calpain, m-calpain and their endogenous inhibiting protein-calpastatin, all of these interact and regulate and control meat tenderness after slaughter. Apart from cattle variety and age, beef tenderness is also significantly influenced by treatments, such as chilling and suspending after slaughter. Our research decides to discuss the effects of stepwise chilling and pelvic suspending on beef tenderness by determining calpains activities, so as to offering mechanisms and technique support on optimizing and changing president chilling methods and suspending.The main results of this experiment are as follows:1. Purification of calpainsFlowrate is 2ml/min, two steps of line gradient elution(First step is 0~215m MNa Cl,second step is 215~500m MNa Cl) can effectively purify calpains. Calpastatin, μ-calpain and m-calpain can be eluted in 98~128 m MNa Cl, 128~150 m MNa Cl and 176~211 m MNa Cl separately.2. The effect of pelvic suspension and stepwise chilling onμ-calpain activityAs the aging time increased, the activity ofμ-calpain in M. Longissimus lumborum sharply decreased; at 48 h and 96 h after slaughter, the μ-calpain activities of conventional chilling group and stepwise chilling group decreased by 15.2%, 21.33% and 89.24, 91.02%respectively, comparing with 1 h; μ-calpain activities of pelvic suspension group and achilles suspension group dropped by 15.4 %, 15.5 % and 85.4 %, 85.8 % respectively, comparing with 1 h. In terms of descending range of μ-calpain activity, pelvic suspension and stepwise chilling have no significant effects(P>0.05). This illustrates that pelvic suspension and stepwise chilling didn’t improve activity of μ-calpain during early stage of aging time.Degradation of calpains system on skeletal protein didn’t play a vital role in improving beeftenderness. As more aging time, μ-calpain is speeding inactivation rate. Therefore,tenderization of μ-calpain is not a main effect.3. The effect of pelvic suspension and stepwise chilling on m-calpain activityAs the aging time increased, the activity of m-calpain in M. Longissimus lumborum sharply decreased; at 48 h and 96 h after slaughter, the m-calpain activities of achilles suspension group and pelvic suspension group decreased by 14.6%, 14.2% and 82%, 87%respectively, comparing with 1 h; m-calpain activities of stepwise chilling group and conventional chilling group dropped by 12.49%, 19.23% and 90.57%, 87.78% respectively,comparing with 1 h. In terms of descending range of m-calpain activity, pelvic suspension has no significant effects(P>0.05). This illustrates that pelvic suspension didn’t improve activity of m-calpain during early stage of aging time. However, stepwise chilling improves activity of m-calpain. Degradation of calpains system on skeletal protein didn’t play a vital role in improving beef tenderness in pelvic suspension. As more aging time, m-calpain is speeding inactivation rate. Therefore, tenderization of m-calpain is not a main effect in pelvic suspension, in contrast with stepwise chilling.4. The effect of pelvic suspension and stepwise chilling on calpastatin activityAs the aging time increased, the activity of calpastatin in M. Longissimus lumborum sharply decreased; at 48 h and 96 h after slaughter, the calpastatin activities of conventional chilling group and stepwise chilling group decreased by 24.34%, 15.04% and 89.4%, 89.57%respectively, comparing with 1 h; calpastatin activities of achilles suspension group and pelvic suspension group dropped by 21.33%, 17.91% and 88.98%, 84.22% respectively, comparing with 1 h. In terms of descending range of calpastatin activity, pelvic suspension has no significant effects(P>0.05). This illustrates that pelvic suspension didn’t improve activity of calpastatin during early stage of aging time. However, stepwise chilling improves activity of calpastatin. As more aging time, calpastatin is speeding inactivation rate. Therefore, stepwise chilling facilitated calpastatin activity, improving the inhabitation on μ-calpain; pelvic suspension has not significant effects on calpastatin activity. |
