Study On The Meat Quality And Physicochemical Properties Between Different Parts Of Normal And PSE Pork Muscle During Postmortem

PSE pork is a kind of typical poor pork, which cause a loss to butchery and meat processing enterprise. But, the formation mechanisms of PSE pork is still have much doubtful point, it's need further study. The test pig is Duroc×Landrace×Yorkshire barrow, choosing the longissimus muscle and biceps femoris are both normal and PSE pork muscle, each has 6 samples. Study the changes of meat quality and the changes of energy substances metabolism and the difference of muscle fiber and proteins. This research can provide references to the pork quality control and PSE formation mechanism.1. The changes of meat quality between different parts of normal and PSE pork muscle during postmortemStudy on the difference of nutritional components(water content, crude fat, crude protein, crude ash) between different parts of normal and PSE pork. The meat quality(pH, centrifuged water loss, shear force, L*) at different time-points(0, 5, 12, 24, 48, 72, 96h) was determined and analyze their correlations. Results indicate that, the water content of PSE pork is significantly higher than normal pork's water content, and the water content of normal longissimus muscle is significantly higher than normal biceps femoris pork muscle's water content(P<0.05); The crude fat of normal longissimus muscle is significantly higher than PSE pork muscle's crude fat(P<0.05). The centrifuged water loss and L* are significantly positively related(P<0.01).The biceps femoris' s pH is higher than longissimus muscle and L* is lower than longissimus muscle in a pig after slaughter. The biceps femoris' s shear force is smaller than the longissimus muscle and the water holding capacity is better than longissimus muscle.2. The changes of physicochemical properties between different parts of normal and PSE pork muscle during postmortemThe energy substances(glycogen, ATP/ADP/AMP/IMP) at different time-points(0, 5, 12, 24, 48, 72, 96h) and the diameter and density of muscle fiber and MFI at time-points(0, 8, 16, 24h) was determined and analyzed energy substances correlations. Results indicate that, the ATP contents of biceps femoris is significantly higher than longissimus muscle during postmortem 2h(P<0.05). The ATP contents is significantly decline during postmortem 8h(P<0.05) the glycogen contents of normal meat biceps femoris is significantly higher than the other groups during postmortem 48h(P<0.05). The change of glycogen and ATP contents are significantly positively related(P<0.01). The density of fiber in PSE pork is denser than normal pork. The change of fiber diameter in PSE pork is smaller than normal pork. The diameter of fiber in biceps femoris is smaller than longissimus muscle. The density of fiber in biceps femoris is denser than longissimus muscle. The rises of MFI in PSE pork is more smaller than normal pork. The MFI of biceps femoris is bigger than longissimus muscle.3. The changes of protein between different parts of normal and PSE pork muscle during postmortempH, centrifuged water loss, protein solubility, CAF activity and SDS-PAGE were determined after slaughter at time-points(0, 8, 16, 24h) and analyzed their correlations. The results show that: The solubility of alloprotein of normal longissimus muscle is significantly higher than PSE pork muscle's(P<0.05). The solubility of sarcoplasmic of normal longissimus muscle is higher than PSE pork muscle's. The CAF activity of biceps femoris is significantly higher than longissimus muscle's. The CAF activity of normal pork is higher than PSE pork muscle's after slaughter in 8 h(P<0.05). SDS-PAGE showed a different pattern of myofibrillar protein in PSE pork and normal pork, but the change of sarcoplasmic protein's SDS-PAGE pattern isn't significantly. Thus, the major protein changes is myofibrillar protein in PSE pork and normal pork, and the degradation of myofibrillar protein of biceps femoris is faster than longissimus muscle's.In conclusion, meat quality of biceps femoris is better than longissimus muscle's, and PSE meat of longissimus muscle is worse than biceps femoris' s. The content of glycogen isn't the basic reason of the formation of PSE meat. The main difference is energy metabolic rate. The energy metabolic rate of PSE pork is quicker than normal pork, and the energy metabolic rate of longissimus muscle is quicker than biceps femoris. SDS-PAGE showed a different pattern of myofibrillar protein in PSE pork and normal pork, and in different parts.