| Since 1990s, China has ranked the first place in the output of mutton all over the world, and the rate for annual growth increased very quickly. Although our mutton products were superior to other countries in the price, the market competitiveness was lower in the international market. One of the main reasons is the lock of the production technologies, such as the standardization and the fresh-keeping technologies.On the other hand, the request of fresh-keeping technologies from the meat manufacturers becomes more and more urgent with the gradual popularization of chilled mutton in native market. So it turns to be pretty necessary to develop the fresh-keeping technologies of chilled mutton. There were many literatures about the endogenous proteases and the quality of chilled mutton after postmortem, but those researches were undergone without any preservative and non of them was done whose samples dealt with any preservatives at abroad. And there was a little, ever non literatures about above conditions in our country. Besides that, the research relatived to the qualities and activities of endogenous proteases and the relationships between them of Nanjiang yellow goat which was reputed one of the best goat breeds for meat in Asia at present was blank.For those reasons mentioned above, Nisin, tea polyphenol (TP) and chitosan, three natural antibiotic materials, were selected and used to do our researches on the inhibition to the main spoilage and pathogenic bacteria in meat, the effect on fresh-keeping of the compound preservatives in chilled mutton and the relationships between the endogenous proteases and the qualities of Nanjiang yellow goat during the whole shelf lives. The aims of this paper were to promote the popularization of chilled mutton and provide the theories for the intensive processing of Nanjiang yellow goat. The main methods taken in this research and the conclusions summarized as follows:1.Three strains of gram-negative bacteria (Escherichia coli, Salmonella enteritidis, Pseudomonas aeruginosa) and six strains of gram-positive bacteria (Staphylococcus aureus, Listeria monocytogenes, Brochothrix thermosphacta, Bacillus subtilis, and two strains of lactic acid bacteria(Lactobacillus pentosus, Lactobacillus plantarum) were selected as indicators of spoilage and pathogenic bacteria in meat. Nisin, tea polyphenol (TP) and chitosan, as the natural antibiotic materials, were used to evaluate the minimum inhibitory concentration (MIC,shown as Table 2-2)of those bacteria (about 106 CFU/ml of each strain) respectively by the serial two-fold agar dilution method. And the optimum combined ratio which was 39.1 mg/L of nisin,78.1 mg/L of TP,469 mg/L of chitosan was determined by the L9(33) orthogonal test based on the MICs.2.Considering about the diffusion of the compound preservatives dip in mutton and on the basis of the preliminary experiment, the compound preservatives dip, containing Nisin 0.625g/L, TP 0.313g/L and chitosan 3.752g/L, was selected to do the fresh-keeping test under packaging preservative film and aerobic condition. The dip was used for the treatment and the untreated mutton was used compared as the control. The control and the treatment samples were analysed periodically for microbiological (total viable count), chemical (pH, TVB-N, water holding capacity and hydrogen sulfide production test), and sensory characteristics. The results indicated that the shelf lives of the control and the treatment were 6 days and 18 days, respectively. The effect of the treatment on the mutton samples was to enable the good quality characteristics to be retained for longer and extend the shelf life 12 days.3.After the determination of their the shelf lives of the treatment and the control, the qualities of the two lots (water holding capacity, cooking loss, pH, shear force, MFI and the total content of free amino acids) and the activities of the endogenous proteases (calpains and calthepsin B, D, L) of Nanjiang yellow goat were detected at day 1,2,3,4,6, 9,12,15,18 after slaughter. Analysed the correlation between the qualities and the activities of the endogenous proteases, the conclusions were just as follows:(1)The correlate relationships between the qualities and the endogenous proteases of the chilled mutton were elucidated as that:There were significant correlate relationships between water holding capacity, cooking loss,pH or tenderness (shear force and MFI) and calpains or cathepsin D (p<0.05,except the relationship between shear force and cathepsin D was r=-0.805 at p=0.100).But not between those qualities and other endogenous proteases, and between pH or total content of free amino acids and any endogenous proteases was also not significant.(2) The correlate relationships between the qualities and the endogenous proteases of the chilled mutton for which the dip was used were elucidated. There were significant correlate relationships (p<0.05) between water holding capacity, cooking loss, pH or tenderness (shear force and MFI) and calpains within day 9 when calpains were activated, but not significant between those qualities and other endogengous proteases except the relatinship between tenderness and cathepsin L during the whole shelf life.Although there were no significant correlation between pH or total content of free amino acids and any endogenous proteases,the relationship was confirmed between the total activites of cathepsins and total content of free amino acids by SDS-PAGE electrophoresis of whole-muscle proteins.(3)The influences, the preservative dip towards the activities of endogenous proteases and the qualities, were ascertained as followed:The dip played a significant inhibition role to cathepsin B and D, but not to calpains and cathepsin L. And it had no significant effect on water holding capacity, cooking loss, pH, tenderness or total content of free amino acids.
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