Effect Of Season,Transport Distance And Lairage Time On Pork Quality

China is one of the word's biggest pork production country,In the past,consumers mainly concerned about safety issues of pork,but now they concern both food safety and quality and sensory characteristics.High-quality pork products is the common goal of slaughtering and processing enterprises.PSE(pale,soft and exudative)pork is the key quality issues that restrict the development of slaughtering and processing enterprises.The occurrence of heterogeneous meat is related to the species.Pigs and poultry have PSE and PSE like meat,while DFD(dark,firm and dry)meat is common for beef.Season,transport distance and lairage time are considered the main pre-slaughter factors for occurrence of heterogeneous meat,Which is associated with post-mortem glycolysis.The rate of glycolysis depends on the rate of ATP depletion and phosphorylation levels.In this study,the effect of season,transport distance and lairage time on meat quality was investigated.1-Effect of season,transport distance and lairage time on 45 min post-mortem pH value and the incidence of PSE porkAt a slaughter house,effect of transport distance and lairage time on pork quality was studied among different seasons.The pigs from different areas were classified according to transport distance,pH value and the incidence of PSE pork was estimated.The results show that the pH at the post-mortem 45 min were significantly lower for summer than those for other seasons(P<0.05).The incidence of PSE pork were significantly higher for summer and autumn than for winter and spring,but the incidence of DFD meat is no significant difference,this indicates that season is an important factor influence the 45 min post-mortem pH value and incidence of PSE pork.In the same season,pH values at 45 min and the incidence of PSE pork significantly differed among transport distance and lairage time points.There was a significant interaction among season,transport distance and lairage time,all of these factors had a significant effect on pH values at 45min.Therefore,the lairage time should be adjusted according to season and transport distance.2.Causes of the post-mortem heterogeneous meatNormal pork,PSE pork,beef and chicken meat samples were taken within 45 min post-mortem,and glycogen,lactate dehydrogenase activity,ATP/ADP/AMP content were measured.Sarcoplasmic proteins and myofibrillar protein from different samples were separated by SDS-PAGE and stained by specific fluorescent dyes Pro-Q Diamond and Sypro Ruby to analyze the density value of each band,identify the different bands,then use the mass spectrometry technical analysis the difference of protein function.The results showed that glycogen level in beef at 45min post-mortem was significantly higher than other three groups,Glycogen content in normal pork was significantly higher than those of PSE pork and chicken(P<0.05).Lactate dehydrogenase activity in PSE pork was significantly higher than other three groups(P<0.05).ATP and ADP content at 45min post-mortem in normal pork was sinificantly higher than other three groups(P<0.05).This indicates that early post-mortem glycolysis rate of beef is lower and followed by normal pork.This is mainly because the pre-slaughter stress accelerated early post-mortem glycolysis rate and LDH activity of PSE pork.SDS-PAGE electrophoresis and mass spectrometry results showed that phosphorylation levels of sarcoplasmic and myofibrillar protein were significantly different and the incidence of PSE pork was related to phosphorylation levels of some glycolytic enzymes.