Effects Of Different Muscle Parts And Different Temperature Treatments On AMPK Activity During Energy Metabolism And Meat Quality Of Beef After Slaughter

AMPK(AMP-activated protein kinase)is a key switch which can control and adjust energy metabolism in the living body even after slaughter.The rate and extent of metabolic especially in the early time after slaughter can greatly affect the quality of meat.This paper studies the effects of AMPK on the metabolism of beef in the early post-mortem,and to further explore the impact of temperature treatment in the early postmortem on AMPK activity and post-mortem meat quality.The experiment determined the change of pH,temperature and energy(including glycogen,lactate,ATP,etc.),metabolic activity(including pyruvate kinase,AMPK)and meat quality differences(water retention,shear force values,etc.),in four part muscles within 24 h after postmortem research in the early post-mortem to explore the effects of AMPK activity on energy metabolism and meat quality characteristics in different parts.In addition,we further study of the effects of different temperature treatments(14 ?,7 ?,0 ?,-21 ?)on AMPK activity,energy metabolism,protease activity and meat quality of Longissimus lumborum in the period of pre-rigor after post-mortem,thus to explore mechanisms of the temperature treatment in the early post-mortem effects on metabolic and meat quality.The results of this experiment are as follows:1.The extent and rate of pH declination of four parts beef muscles within 24 h after slaughter are different,and there are significant differences in ultimate pH24 and holding water capacity,meanwhile,maturation has the differences effect on the four parts of the meat.The meat quality of the four parts can be ranked in the following descending order: PM >LD> SK > SM.2.The initial energy level after slaughtered can affect metabolic rate and extent of beef parts meat.ATP content and the(AMP + IMP)/ ATP ratio at 1.5h post-mortem can affect AMPK activity,thus affect the start of metabolism and metabolic rate after post-mortem.The initial content of glycogen at 1.5h post-mortem can affect the extent of metabolism and affect ultimate pH.3.AMPK can regulate glycolysis rate through regulating the activity of key enzyme after post-mortem.The time points of pyruvate kinase reaching the maximum activity and the maximum activity values of four part muscles are different.AMPK activity of PM was significantly higher than LD,and its time points of pyruvate kinase reaching the maximum activity and the maximum activity values earlier than and higher than LD.In addition glycolytic rate and pH decline rate of PM is significantly faster than LD.The experiments indicate that AMPK is involved in glycolysis,and affect glycogen breakdown,lactic acid accumulation and pH decreases,thereby affect water holding capacity and tenderness et..4.The different temperature treatments can significantly affect the rate of temperature and pH decline,but to 24 h post-mortem,the temperature and pH24 difference was not significant.The water holding capacity,maturation rate and tenderness are different among four temperature treatments.All above,the meat quality of the four treatments can be ranked in the following descending order: 14?>7?>-21?>0?.5.The initial content of glycogen at 2h postmoterm of four temperature treatments was not significant,but the rate of glycogen breakdown is different in the early post-mortem.The amount of glycogen breakdown and lactic acid accumulation at 24 h post-mortem was not significantly different.6.Different Temperatures can affect the time point of AMPK activity reaching the maximum,while can't affect on the maximum value of the activity significantly.PM reaches the maximum at 2h post-mortem,and LD reaches its maximum at 4h post-mortem,but the difference of maximum value between them was not significant.Similarly,the time point of pyruvate kinase reaching the maximum activity in the AMPK action is different,but the value of the maximum activity was not significantly different.The results showed that different temperature treatments in the early postmortem can affect the rate of glycolysis,but does not affect the extent.So the rate of glycolysis has an effect on meat quality more obviously.