Role Of Lactate Dehydrogenase In Metmyoglobin Reduction And Color Stability Of Chilled Beef Longissimus Dorsi

Flesh color is an important indicators for consumer to determinethe freshness and shelf life of meat,the browning of the surface of cooling meat is perceived by the consumer as a deterioration of the quality.In this experiment,the cooling beef under aerobic storage conditions was used as test material to investigate the changes of the main biochemical factors affecting the color stability of meat and the relationship between LDH activity and MRA activity.The relationship between lactate dehydrogenase and metmyoglobin reduction and the color stability of flesh was clarified by the biochemical mechanism of stabling myoglobin redox form,revealing the mechanism of lactate dehydrogenase in the stability of beef and the metmyoglobin reductioncombined with studies of hatching in vitro.The results are as follows:1.The L * and b * values of the three groups of cooling beef during the postslaughter period showed a tendency to increase first and then decrease,and there was no obvious change in 1 3 days.The L * and b * values of the inhibition group were respectively2.26% and 6.79% lower than the initial values,while the L * values of the control group and the activated group were increased by 3.47% and 4.46%?P <0.05?,respectively,The a* values in the control group,the inhibitory group and the activated group decreased by 17.5%,25.23% and 2.35%?P <0.05?during the refrigeration process.2.In the early stage of cold storage,the myoglobin was mainly existed in the form of OMb?about 56%?.,the OMb decreased to 10.93% and the MMb increased to 68.90% after 7 days?P<0.05?.In addition,the LDH Activity,NADH concentration and Met Mb R activity were significantly decreased by 45.96% 27.81% and 84.64%?P <0.05?compared withthe initial staterespectively,resulting in a large accumulation of MMb.3.The activity of LDH and the concentration of NADH in muscle treated with sodium oxalate inhibitor were significantly decreased?P <0.05?,while significantly increased treatment with betaine?P <0.05?.The results showed that sodium lactate could effectively inhibit the activity of lactate dehydrogenase in muscle tissue,which resulted in the decrease of NADH concentration and Met Mb R activity,which affected Met Mb reduction,thus reducing the color stability of the flesh meat.The betaine was opposite.4.SDS-PAGE analysis showed that the expression of LDH₁ isoforms in the control group was significantly higher than that in the treatment group 1,which was significantly lower than that in the treatment group 2?P<0.01?.The results showed that sodium oxalate could inhibit the activity of LDH-B and inhibit the expression of LDH1 protein and decrease the rate of NADH production in muscle tissue.resulting in a decrease in Met Mb R activity and affecting Met Mb reduction,and thus reduce the stability of the flesh meat.the role of betaine in the opposite.5.Metmyoglobin reductase activity is not obvious in the Lactate-LDH-NAD⁺ system in the absence of reaction mixture including bovine muscle extract?LDH?,NAD⁺ or lactate,The addition of L-lactate to the replacement of D-lactate or the addition of sodium oxalate to the mixture resulted in the absence of metmyoglobin reduction,the metmyoglobin reduction ability was increasedsignificantly with an increasement of the amount of bovine muscle extract,the NAD⁺ or lactate concentration and an appropriate increasement of p H and reaction temperature in the mixture,There was no difference in the metmyoglobin reduction ability with potassium lactate in place of sodium lactate in the mixture?P>0.05?.it is confirmed that lactate dehydrogenase was involved in Met Mb reduction and while the interaction of L-lactate and NAD⁺in vitro experiments.