Effect Of Changes In Myocyte Mitochondrial Electron Transport Chain On Color Stability Of Cooled Qinchuan Beef In Storage

Meat color is one of the most important factors influencing economic value,and is influenced by several biochemical processes in postmortem muscles.In this paper,the changes of mitochondrial electron transport chain(ETC)of the longissimus dorsi muscle of Qinchuan beef during post-slaughter storage(0-4℃)under the interruption of aerobic respiration and blood circulation were investigated and correlated with the changes of meat color.To reveal the effect of mitochondrial electron transport chain changes on meat color from the molecular level,the results of the study were as follows:1.The relative contents of pH,L*,a*,b*,Deoxymyoglobin(DeoMb),Metmyoglobin(MetMb),Oxymyoglobin(OxyMb),and the relative contents of MetMb reductase activity(MRA)and reductive coenzyme Ⅰ(Nicotinamide adenine)were determined during low temperature storage at 0-4℃ using chilled Qinchuan beef at different storage periods.The relative contents of DeoMb,MetMb,OxyMb,MRA and reduced coenzyme I(Nicotinamide adenine dinucleotide(NADH)were analyzed and the trends were observed.The results showed that the pH value decreased and then increased with the increase of storage time,and then decreased to the lowest value at 4 d after slaughtering;the L*value increased and then decreased,the a*value,MRA and NADH decreased gradually,and the b*value increased gradually;the OxyMb decreased significantly with the increase of storage time,the relative content of MetMb increased significantly,and the DeoMb did not change significantly.The changes in the relative content of Mb derivatives were significantly correlated with pH,meat color,MRA and NADH content,indicating that OxyMb was gradually oxidized to MetMb during post-slaughter storage,and the reduction of reducing substances led to the inability of MetMb to be reduced,thus causing meat discoloration,which was influenced by the content of reducing substances and changes in muscle pH.2.The structural and functional changes of the mitochondrial inner membrane of chilled Qinchuan beef myocytes during different storage periods and the intrinsic relationship between them and meat color were investigated.The mitochondrial membrane permeability,electron transport chain complex Ⅰ,Ⅱ,Ⅲ and Ⅳ activities,ATP content,superoxide dismutase(SOD)activity,glutathione peroxidase(GSH-Px)activity and catalase(CAT)activity were measured.The results showed that the mitochondrial membrane permeability continued to increase with increasing storage time;the mitochondrial electron transport chain complexes Ⅰ,Ⅱ,Ⅲ and Ⅳ,as well as ATP,SOD,GSH-Px and CAT decreased significantly;MDA increased significantly;the relative content of Mb-derived ecology,meat color indexes and mitochondrial membrane permeability,mitochondrial electron transport chain complexes Ⅰ,Ⅱ,Ⅲ and Ⅳ activities,as well as the relative content of Mb derivatives,meat color indexes and mitochondrial membrane permeability,mitochondrial electron transport chain complexes Ⅰ,Ⅱ,Ⅲ and Ⅳ activities,as well as ATP,SOD,GSH-Px,CAT activities and MDA content were significantly correlated,indicating that the failure of the antioxidant system and the accumulation of MDA in Qinchuan beef during post-slaughter storage caused damage to the mitochondrial structure,resulting in a gradual decrease in the activity of the complexes located in the inner mitochondrial membrane with prolonged storage time,affecting the activity of the reductase system in muscle,resulting in a decrease in the reducing power of MetMb.This resulted in the continuous accumulation of MetMb,which eventually led to the browning of meat color.3.To investigate the effect of mitochondrial electron transport chain on meat color formation in chilled Qinchuan beef during storage,a proteomic approach based on 4D-LFQ technology was used to identify four significantly different proteins associated with the mitochondrial electron transport chain,namely ATP5F1D,ATP5F1C,NDUFB5 and NDUFA4,which affected meat color through energy metabolic processes and redox processes.They affected the meat color through energy metabolism process and redox process by influencing the redox enzyme activity.In conclusion,the failure of the antioxidant system and the accumulation of MDA in Qinchuan beef during post-slaughter storage caused the disruption of mitochondrial structure,resulting in the disruption of the expression of complex subunits such as ATP5F1D,ATP5F1C,NDUFB5 and NDUFA4,which contributed to the reduction of mitochondrial complex activity,resulting in the energy metabolic process and redox process,and further influenced the muscle.The redox status of MetMb was further affected,resulting in the continuous accumulation of MetMb,which eventually led to the browning of meat color.