Comparative Studies On Biochemical Characteristics Between Normal And PSE Pork Muscle And Studies On The Technology Keeping Pork Freshness

Post-mortem rapid glycolysis of pork and slow cooling of the carcass lead to muscle higher temperature(≥38℃) and lower pH (≤6.0), consequently, bring the cisterna burst-apart, sarcolemma tissue fragility and decrease in density. the water holding capacity decreases after the denaturation of myosin, , then PSE meat is engendered.PSE is the usual defect on pork quality. It is mostly examined by sensory access, and it is necessary to utilize the biochemical characteristics of muscle to find a high sensitive and specialized analysis means to research the quality of pork. It can offer better theory to domestic pork industry and good technology instruction to meat product process industry.Fresh pork is rich in nutrition and a good media for microorganism's growth. It is easy to decay without relevant measures. Therefore, enhancing studies on technology to keep pork freshness and prolonging the shelf-life are very important.The differences between PSE and normal pork were showed in this study by comparing the biochemical characteristics of myofibrils and myosin; meanwhile, the effect of coating preservation technology on fresh pork quality were discussed bymeans of the biochemical characteristics analysis. The results as follow:1. Comparative studies on myofibrils morphology of PSE- and normal pork muscleThe myofibril fragmentation index, morphology, sarcomere length and water-holding capacity were compared between normal and PSE pork. The results showed: the fragmentation of sarcomere occurrenced in I band, the fragmentation index would increase with the increasing of homogenizing time and storing time at 5 ℃ .The fragmentation of PSE was acuted in the first two days, whereas the fragmentation of normal pork was apparent in 2⁴ days. The changes of myofibril fragmentation were consistent in normal and PSE pork, which showed the temperature was more influential than time and the fragmentation of normal pork myofibril is more sensitive than PSE pork . Myofibril was destroyed badly by the temperature, it was probably the results of combined action of protein denaturation and proteolysis. The sarcomere of PSE was always shorter than that of normal pork because of the partial denaturation of PSE myosin. In the same time, the water-holding capacity of PSE pork was lower than normal pork , but the tendency was consistent; with the increasing of storing time at 0 °C ,the denaturation of myofibril protein went acuter and the water-holding capacity went down continuously.2. Comparison of thermostability of myofibrillar ATPase from PSE- and normal pork with freshwater fish muscleThe objective of this study was the comparison of thermo-stability of myofibrillar ATPase from PSE- and normal pork with freshwater fish muscle. When the myofibril suspending solution was stored at 35℃ for varies time and at different temperature for 30 minutes we studied the Ca²⁺-ATPase activity.The results indicated: with the increasing of ion-intensity ,the special activities of myofibrillar Ca²⁺-ATPase decreased; but in the same ion-intensity, Mg²⁺-ATPase> Ca²⁺-ATPase. the Ca²⁺, Mg²⁺-ATPasse relative activities of fish muscle are higher than pork muscle, the Mf ATPase activity of normal pork muscle is higher than PSE pork muscle.With the increasing of incubation time and temperature the myofibrillar Ca²⁺-ATPase activitydecreased .however ,the effect of temperature on myofibrillar Ca2+-ATPase activity was more apparent than incubation time. At 45 °C, the myofibrillar Ca2+-ATPase first order inactivatity rate constants(KD) of cold blooded animal (fish)was larger than warm blooded animal(pork), thermo-denaturation of silver carp myofibrillar protein was the worst, thermo-stability of the normal pork was the best. So it can be used as a characteristic parameter to distinguish the muscle species.Reaction activation energy^ Entropy% Enthalpy were figured out by Arrhenius equation. From the results we can know that the thermodynamic parameters of cold-blooded animals—fish were significantly different from those of warm-blooded animals—pig, Crucian carp and Silver carp were more sensitive to the variety of temperatures than normal pork and PSE pork, the inactivation thermaodynamic parameters in the same species were that normal pork exceeded PSE pork and Crucian carp surpassed Silver carp. Furthermore, it may only be applied to the comparation of the same species that the thermodynamic parameters calculated by Arrhenius equation determined the effects of temperature on ATPase inactivation rate.3. Comparative studies on myofibrillar protein extractability and water-holding capacity from PSE and normal porkThe results indicated the myofibrillar protein extractability, total -SH and water-holding capacity from PSE were lower than normal pork. The denaturation of sarcoplasmic protein from PSE and normal pork was not apparent. The water-holding capacity was high correlation with the extractability of myofibrillar protein during 6-7 days storage at 0"C. The myofibrillar protein extractability can be used as the important index to distinguish PSE and normal pork.4. Comparative studies on biochemical characteristics of actomyosin between normal and PSE pork muscleThe objective of this study is to investigate the comparison of biochemical characteristics between normal pork muscle and PSE. The results indicated that the thermal denaturation of PSE was more sensitivity than normal pork, the -SH ,ATP sensitivity and superprecipitation showed high correlation. The -SH and ATP sensitivity can be used as a useful index to distinguish PSE and normal pork.5. Comparative studies on proteins between PSE and normal pork muscle by SDS-PAGE.The objective of this study is to determine the differences between PSE and normal pork by SDS-PAGE electrophoresis figures of actomyosin and sarcoplasmic. The results suggested that there was no difference between both sarcoplamic electrophoresis figure, that is to say,the sarcoplasmis didn't reduce apparently;but there was a considerable difference between both actomyosin electrophoresis patterns, it may be that this difference raised from the troponin-T degration of PSE meat. When PSE and normal pork were stored at variant temperature, there was no difference in sarcoplasmic electrophoresis patterns, and a considerable difference in actomyosin electrophoresis patterns, especially between PSE and normal pork muscle . Some electrophoresis bands disappeared at various temperature storage.This phenomenon indicated some protein of actomyosin would degraded with the decrease of meat freshness, but which protein chains degration needs further research.6. Effect of different protein denaturation protector on pork proteins.Edible glycerol, sorbitol (protein protector) and protein denaturant tannin, SDS is taken to discuss the effect on mofibrils theoretically. The results suggest that:(1) Adding protein denaturation protector is better than not, and sorbitol is more effective than glycerol.(2) Adding protein denaturant will accelerate the denaturation of myofibrils, and the effect of SDS is larger than tannin.(3) The suspending liquid of myofibrils of pork muscle stored at 4°C, adding sorbitol and glycerol respectively, the remaining ATPaes activity is a little higher than that without protector.However, adding tannin and SDS, the remaining ATPase activity is obviously lower than that without denaturant.7. Studies of coating-film agent on pork meat.Film-coating freshness-keeping that formed a protective film on the surface of pork was to prevent microorganism from invading, and kept the pork extract from running away, and stopped the meat color from dark. The results indicated that taking...