| China is a big country in pork consumption,and the proportion of pork consumption accounts for more than 65% of the national meat consumption.In recent years,with the development of China's economy and the improvement of people's income level,high-quality,pollution-free,green,organic and high-grade pork consumption has gradually become the trend of development.How to maintain the nutritional quality of pork and prolong its shelf life has become one of the new hot spots in the research of meat products.Taking fresh pork as the research object,the pork samples pH value,TVB-N content,TBA value,the content of salt soluble protein,total bacteria,coliform,drip loss,texture(hardness,elasticity,chewiness and resilience),color(a* value,b* value,L* value)to as a fresh and sensory index were detected by electronic nose of pork during storage and odor,principal component analysis.The effects of different packaging materials on the quality of frozen pork,the quality changes of pork under the condition of frozen storage and cold storage,the quality of pork under different freeze-thaw temperatures,and the effect of different preservatives on the quality of frozen pork were studied.It provides theoretical support for the field of pork preservation.The main contents and conclusions are as follows:1.The effects of three barrier materials on the pork quality,such as PE,PVDC and PP /PE / Nylon,were compared under the condition of-18 ?,so as to identify the most suitable packaging materials for pork preservation.The results showed that with the extension of storage time,three kinds of pork packaging materials with different barrier property,the content of TVB-N,TBA value,drip loss rate showed a rising trend,the content of salt soluble protein,total number of colonies,elasticity,resilience,a* value decreased,pH value,hardness and chewiness showed the first decline after rising trend.The fresh-keeping period of pork without packaging is only 6 months.The fresh-keeping period of pork in PE,PP / PE / Nylon is 9 months and 10 months respectively,while the preservation period of pork in PVDC packaging material can reach 1 years.The order of the fresh-keeping effect of the three kinds of packaging materials for frozen pork is: PVDC > PP / PE / Nylon > PE.The high barrier PVDC packaging material has the best preservation effect on frozen pork,and themiddle barrier PP / PE / Nylon packaging material is next,and the low barrier PE packaging material is the worst.2.the changes of two kinds of packaging materials of PE and PVDC were compared to the quality of pork in-1.5 centigrade and 3 degrees centigrade,in order to determine the most suitable storage method for pork preservation.Results: with the prolongation of storage time,the content of TVB-N,coliform group,and juice loss rate of pork in cold storage and microfreeze storage showed a trend of rising.The content of salt soluble protein,hardness,elasticity,chewiness and resilience showed a downward trend,and the value of pH showed a trend of decreasing and then rising,and the a* value presented.The tendency to rise and drop first.The change trend of cold storage group(3 ?)and micro freezing group(-1.5 ?)was very significant,but different packaging materials had little effect on the quality of pork under cold storage and freezing storage conditions.Pork stored at 3 C refrigerated condition had better quality in the early storage stage,but the shelf life was shorter,only 6D.Under the condition of cold storage,the fresh keeping effect of pork is limited,and the fresh keeping period of pork can reach 24 D under the condition of-1.5 centigrade.The fresh keeping period is 4 times of the cold storage condition.The pork has a good quality in the fresh keeping period,and the pork is better than the cold storage.3.The quality of pork was studied under three kinds of micro freezing storage conditions at-1,-2 and-3,respectively,to determine the most suitable temperature for pork preservation.The results showed that with the extension of storage time,different micro freezing temperatures of pork,the content of TVB-N,coliform,drip loss showed a rising trend of salt soluble protein content,hardness,elasticity,chewiness and resilience decreased,the total number of colonies,PH value decreased first and increased later the trend,a* value first increased and then decreased.Under the condition of-3 ?,the quality of pork was obviously better than that of-1 and-2?,and there was no significant difference between-1 and-2.However,under the condition of-3 freezing,the loss of pork juice was slightly heavier,which may be due to the more ice crystals produced in pork at-3 ? and the mechanical damage to the muscle cell membrane,but the overall juice loss is not serious.The pork can be kept fresh to 24 day under the condition of-1 ? and-2 ?,and the pork can be kept fresh to 26 day under the condition of-3?storage.The storage conditions at-3 ? were better than that of-1 and-2,which could delay the spoilage and deterioration of pork.4.The effects of nisin,natamycin and lysozyme on three kinds of preservatives on pork quality were studied under the condition of-3 freezing,and the most suitable preservative for pork preservation was determined.The results showed that with the extension of storage time,after the three preservatives of pork,the content of TVB-N,coliform,drip loss,b*valueincreased,hardness,elasticity,chewiness and resilience decreased,the total number of colonies,pH showed decreased and then increased trend,a* value,L* value first increased and then decreased.The pork treated with lactostreptococcin,namycin and lysozyme accords with the national standard of pork hygiene in the 32 day,32 day and 34 day respectively,and the index is better than that of the control.The preservation period of pork is longer than that of the control group by 6 day,6 day and 8 day respectively.The preservative agent had an obvious effect on the preservation period of pork under the condition of freezing.Among them,the fresh-keeping effect of lysozyme was the best,and nisin had the same effect as namamycin. |
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