Effect Of Different Chilling Methods On Caspase-3, 9 Activity And Tenderness Of Beef Longissimus During Postmortem

Calpain can improve tenderness of Houhesitan bulls on postmortem, but μ-calpain is not primary role for different chilling methods on postmortem for muscle tenderization of Houhesitan bulls. In order to investigate the mainly reasons of tenderness differences under different cooling methods on postmortem and clarify caspase enzymes and tender process of mutual relations. According to the three-stage cooling maturity model of regulating the metabolic rate of ATP after slaughter cattle and the study using the three cooling model to determine the p H, ATP/ADP/AMP, sarcomere length, shear force, myofibrillar fragmentation(MFI); the research focused on western blotting to determine the decomposition fragments of the caspase3/9 and its substrate PARP; and using the fluorescence quantification to determine the caspase3/9 activity; and using the i TRAQ method to track the proteome map in improved tenderness process of different chilling methods during the postmortem. The results are as follows:(1) The results indicated that the p H of treatment was significantly lower than the control at 8,12 and 24 h postmortem(P < 0.05). Sarcomere length and ATP was much greater in treatment group than control group at 4 h and 8 h postmortem(P < 0.05), respectively. The MFI of treatment was significantly higher than the control(P < 0.05). The shear force of treatment was lower than the control(P < 0.05) on days 1, 7, 14, 21 postmortem(P < 0.05). The results suggested that 3-step chilling method may improve the tenderness of M. longissimus lumborum in Holstein bulls and improve quality of Holstein bulls compared to the traditional three-stage chilling method.(2) The 35 k Da pro-Caspase-3 were splited into 18 k Da fragments, 37 k Da of pro-Caspase-9were decomposed into 23 k Da fragments and the 113 k Da of PARP were splited into 24 k Da in the treatment group and the control group during the initial stage postmortem. And the ratio of shearing force at 48 h and caspase 9 activity at 8 h and 12 h in treatment group was significantly lower than control group(P < 0.05). The ratio of shearing force at 48 h and caspase 3 activity at 8, 12, and 24 h in treatment group was significantly lower than control group(P < 0.05). The results suggested that caspase enzymes involved in the tenderness process of Hesitant bulls compared with the conventional cooling method, caspase-3/9 activityplayed a greater role in the three-stage cooling method on the process of tenderness.(3) The three-step cooling and traditional 4℃ cooling model were labeled with the i TRAQ reagents. The results showed that the peptide library with bovine protein matches were 15125,identification of bovine proteins were 1740, the difference between three-step cooling and traditional 4℃ cooling protein were 57, and associated with the skeletal muscle fibrils protein were 12. The study was first established the total protein profile of Holstein bulls under different chilling methods on postmortem. Using the network resources databases to identify differences in protein molecular function, biological process and analysis of metabolic pathway.The results suggested that differences expressed protein were high proportion in cell signaling pathways and myofibrillar protein breakdown pathway. Moreover, The experiment found other differences proteins that was not caused by different chilling methods,and there may be a difference in their own self-degradation, it will become a potential research directions.