Study On Effects Of Degree Of Slaughter Bleeding On The Response Mechanism Of Beef Color Change During Storage

Color stability is one of the important characteristics of meat and meat products.It is the primary quality atribute seen by the consumer,who may use it as an indication of freshness and wholesomeness.In complete bloodletting carcasses,due to the low hemoglobin content,the effects on flesh color are very limited and are usually not considered.Myoglobin is the most prominent color protein in the flesh color,which directly determines the color and stability of the post-mortem carcass.The difference in the degree of bleeding will cause the muscle cells to enter anaerobic respiration different timings,so that intracellular biochemical changes have different effects on flesh color.Most of the studies on the color changes focuses on the influence of external factors.There were more studies on the main internal biochemical factors of meat color.However,there were few studies investigating the main intracellular biochemical changes and their interrelationships related to color during storage.In this paper,Raman spectroscopy technology and cell biology research methods were used to study the interaction between changes in color and the changes of mitochondria,reducing substances,and enzyme activities during the storage of beef with different degrees of bleeding to reveal the molecular mechanism of changes of beef color.To provide theoretical guidance for the development of color preservation and preservation technology in beef storage.The research content and conclusions were as follows:(1)The response of color changes to the bleeding degree in beef during storage was studied.The changes in the relative contents of Mb,MbO2,MetMb,NADH content,lactic acid content,lactate dehydrogenase and myoglobin reductase activity were determined.The result showed that the a*gradually disappeared and gradually darkened during storage.The stability of bleeding 90%a*was significantly higher than the bleeding 80%and 70%.The L*and a*values were significant positive correlation between deoxymyoglobin and oxymyoglobin.MetMb was a significant negative correlation between L*and a*.The linearity of the oxidation state of myoglobin and meat color with storage time was better in the food quality function in the 0-level and the 1-level mode.The myoglobin oxidation rate of bleeding 90%was lower than bleeding 80%and 70%,and the stability of color was relatively best.(2)The response of muscle cell mitochondria changes to the bleeding degree in beef during storage was studied.The result showed that with the increase of storage time,the damage degree of mitochondrial structure increased and the function gradually decreased.Kinetic analysis showed that the damage rate of mitochondrial structure and function of bleeding 90%beef was the lowest.There were significant differences in the changes in ultrastructure and collapse of external appearance.The main manifestations of mitochondrial structural damage were increased membrane permeability,abnormal morphology and size of mitochondria,and decreased number of mitochondria leading to loss of enzyme activity and decreased metabolite content.The free radicals in the body could not be eliminated in time,and gradually accumulated.The ions were very active and easily bind to the polar residues and non-polar residues in the myoglobin molecule,so that the hydrophobic regions in the molecules were "hidden ".The reduction of the protective effected on the oxidation of Fe2+,thus affecting the reversible binding of Fe2+ and O2,ultimately resulting in the inability of the MetMb to be reduced to oxymyoglobin.From the cytological level,the microscopic mechanism of color change in beef with different bleeding degrees was revealed.(3)A method for the determination of beef myoglobin content based on Raman spectroscopy was established.By comparing the modeling results of different methods of rejecting abnormal samples,sample set partitioning methods,quantitative analysis methods,spectral pretreatment methods,characteristic wavelength selection and model suitability maintenance methods,it was concluded that the mass-adjusted calibration model has better prediction results than the local calibration model for different degree of slaughter bleeding of beef(Mb:R2P =0.767,RMSEP=2.056;MbO2:R2p=0.774,RMSEP=1.762;MetMb:R2p=0.725,RMSEP =2.163).And Raman spectroscopy can be used to detect beef myoglobin content.(4)The response of the structure of myoglobin changes to the bleeding degree in beef during storage was studied.Comparison of the peak intensity and the peak displacement information of Raman spectra at different storage times,and the redox status of myoglobin was assigned with reference to the functional group standard table.The result showed that with the increase of storage time,the content of a-helical structure of beef myoglobin gradually decreased in three degrees of bleeding.The content of irregular curl gradually increased,and the content of P-sheet first increased and then decreased,while the content of P-angle decreased first and then increased.The trend of changes showed that the structure of myoglobin in beef was transformed from regular to loose.The lower degree of bleeding was associated with the more obvious looseness of the structure.The myoglobin disulfide bonds gradually changed from g-g-t configuration and t-g-t configuration to g-g-g configuration.Among them,the g-g-g configuration with 90%of blood was relatively the lowest,and the g-g-g configuration with 70%of blood was the highest.The bleeding degree was well,the myoglobin configuration was more stable.The 1850/1830 and N bursts/N pack values showed a trend of increasing first and then decreasing,and the lower the degree of bleeding,the larger the 1850/1830 and N burst/N pack values,indicating that the better the bleeding degree,the tyrosine residue.Tyrosine residues were buried in protein molecules,the hydrophobicity of the myoglobin molecule was reduced,and the reversible binding of Fe2+ to O2 could not be guaranteed,so that the rate of reducing the MetMb to oxymyoglobin was reduced.The oxidation status of myoglobin was strongly correlated with the secondary structure of the protein,the amount of exposed tyrosine and tryptophan residues,and had a significant effect on flesh color and its stability.From the protein secondary structure level,the microscopic mechanism of color change in beef with different bleeding degrees was revealed.In summary,the present study studied the changes in the color of beef during storage,the relationship between changes in mitochondrial ultrastructure of muscle cells and changes in color,the effects of reducing substances and reductase activities produced during storage on the change of flesh color.From the two aspects of cytology and protein secondary structure,the microscopic mechanism of color change in beef with different bleeding degrees was revealed.