| Chilled pork have been not only soft and elastic texture, but also delicious and nutrient-rich. Because of its economy and convenience, chilled pork is becoming more and more popular. However, during the processing and trade, the growth of micro-organisms of the chilled pork brings spoilage and brown spot, it seriously reduces the shelf life of the chilled pork. These problems greatly effect the popularization of chilled pork. In order to prolong the shelf life of chilled pork, many experts have dedicated their researches on preservation method. At present, these methods include preservative treatment, air modified packaging and irradiation technology. But it is not easy to control the proliferation of micro-organisms and the physical or chemical changes of the chilled pork by virtue of any a single method, so a comprehensive preservation is necessary to take full use of the advantages of various methods.In this study, the variation of total bacteria in chilled pork, hot pork and the incipient microflora in chilled pork were analyzed, three preservatives were selected from a variety of natural preservatives for chilled meat, and a complex formula was developed. And the synergic action of natural complex preservative with modified atmosphere packaging was preliminary studied.(1)The microflora of hot pork and chilled pork was analyzed. The results showed that the total bacteria of chilled pork was significantly less than hot pork, and the final total bacteria of chilled meat with two kinds of packaging has significant differences (a<0.05). And it was showed that whether the equipments were sterilized completely or not and the cross contamination between the equipments were the most important factors that effect the shelf life. They determine the incipient microflora, so it was advised to focus on the management in the production process to ensure the quality and shelf life of meat. The results of microflora analysis of chilled meat are as follows: Pseudomonas was the dominating species among the incipient micro-organisms of chilled meat and its logarithm was 4.15, total bacterial logarithm 4.28, Brochothrix thermosphacta logarithm 2.96, Enterobacteriaceae logarithm 2.19, lactobacillus logarithm 2.12, Staphylococcus and Micrococcus logarithm 1.81, mold and yeast logarithm was rarely detected (<1).(2) The screening test among lysozyme, natamycin, lactoferrin, Nisin, and tea polyphenol was done, based on Minitabl4,5 factors 1/4 fractional factorial design implementation, and Nisin, lysozyme, lactoferrin was selected for the following study. The minimum inhibitory concentration of the three natural preservatives was determined by virtue of agar diffusion method; The minimum inhibitory concentrations of Nisin were as follows: 0.01% for lactobacillus,0.02% for Staphylococcus aureus; he minimum inhibitory concentrations of lysozyme were: 0.02% for lactobacillus,0.01% for Staphylococcus aureus,0.08% for E. coli, and the minimum inhibitory concentrations of lactoferrin are: 0.20% for E.coli,0.20% for Staphylococcus aureus, and 0.40% for Pseudomonas. And the optimal conditions of preservatives were obtained by four factors and two levels response surface analysis using Minitable 14 statistics analysis software. The optimal composition rates were: Nisin 0.28%.lysozyme 0.46%, lactoferrin 0.60%, pH 5.16. After disposal with such natural complex preservatives, the chilled pork could stored for 15d.(3) After treated with the complex preservatives, the pork was packed with different ways, and then stored at 0-4℃, to test the variation of micro-organisms, physical and chemical index. It showed that complex preservatives combined with modified atmosphere packing had obvious synergies on chilled pork. Under the condition of logarithm of bacterium 4.27, the shelf life of chilled pork with vacuum packing was 15 days.But the disadvantage of the vacuum packaging was that chilled pork during storage would turn dark purple, not naturally red, however the meat could still remain natural red, after vacuum disappeared.
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