Study On Spoilage Microorganism And Natural Preservatives For Preservation Of Chilled Mutton

In this thesis, the dominant spoilage microorganisms of chilled mutton made in Tacheng district were isolated and identified.The composition of the initial microflora and changes of microflora during storage under vacuum were analyzed. The antibacterial activities of nisin, tea polyphenols,chitosan, the extraction of clove and cinnamon were compared and the optimum combinations of the five natural preservatives for the preservation of chilled mutton were researched by using the response surface methodology.The effects of the optimum combination of the five natural preservatives for the preservation of chilled mutton were also researched. The results included several parts as follows:1. Eleven strains dominant microorganisms of chilled mutton made in Tacheng were isolated and preliminary identified. They were Cedecea lapagei, E. fergusonii, Enterobacter aerogenes, L. plantarum, L. rhamnosus, P. fluorescens, P. paseudoalaligenes, two strains Brochothrix thermosphactas ,one strain Staphylococcus and one strain Yeast.2. Pseudomonas, Lactobacillus, Staphylococcus, Enterobacteriaceae and Brochothrix thermosphacta were the dominant microorganisms in the chilled mutton made in Tacheng district. Lactobacillus increased progressively and became predominant microflora during storage in 4℃under vacuum; Enterobacteriaceae and Brochothrix thermosphacta increased slowly, but Staphylococcus decreased gradually.3. Effective antibacterial effects of nisin, tea polyphenols,chitosan, the extraction of clove and cinnamon were found based on single factor experiments.The optimization of the combination of the five natural preservatives was focused on the preservation of chilled mutton by Response surface methodology. Quadratic polynomial equation was obtained through multiple regression analysis. The predicted model was proven adequate when tested by the lack of fit and coefficient of determination (R2). The results revealed that antibacterial effects of tea polyphenols were more positive than that of chitosan, the extraction of clove and cinnamon, and nisin. There was a significant synergy between tea polyphenols and the extraction of clove and cinnamon (p <0.01). The results of regression analysis showed that the optimum proportion of the combination of nisin, tea polyphenols, chitosan and the extraction of clove and cinnamon was 0.117%, 0.243%, 1.16% and 4.19% respectively.4. The effects of the optimum combination of the five natural preservatives for the preservation of chilled mutton were evaluated. The results revealed that shelf life of vacuum packaged chilled mutton, stored at (3±1)℃and treated using the compound natural preservatives solution by soaking treatment and brushing packaging bag treatment, were 16 days and 11days respectively, while the contrast could preserve 7 days. The compound natural preservatives were proved effective for the preservation of chilled mutton.