| In this paper, the major spoilage microorganisms in pasteurized milk were isolated and purificated by using different selective culture medium, and identified by colony morphology and physiological and biochemical tests. and the results showed that Pseudomonas, Enterobacteriaceae, lactic acid bacteria, yeast, Micrococcus and Staphylococcus were the major spoilage microorganisms. It was preliminary isolated and identified two genus of Pseudomonas, Enterobacteriaceae and yeast and one genus of Lactobacillus, Lactococcus, Micrococcus and Staphylococcus. It showed that Pseudomonas, Enterobacteriaceae, lactic acid bacteria were the major organisms responsible for spoilage.The number of microorganism determined by using the flat colony counting method, and established the growth curves of the major spoilage microorganisms in pasteurized milk at different storage temperatures. The results showed that the total of bacterial and all kinds of bacteria increased inordinately. In general,pseudomonas, lactic acid bacteria and enterbacteriaceae grew the fastest at all researched temperatures, the number of pseudomonas, lactic acid bacteria and enterbacteriaceae were close to the numbers of bacteria. The number of Yeast , Micrococcus and Staphylococcus were also inceased at these temperatures .Aerobic plate count on pasteurized milk under various storage temperatures 4℃,10℃,15℃and 20℃were monitored succession. Growth models of Aerobic plate count at different temperatures using SAS9.1 software were indicated that the growth dynamics of Aerobic plate count could be well described by a Gompertz type model, the R-square increased with the temperature and more than 0.9. The modle of relationship between temperature and maximum specific growth rate, lag phase were built respectively using Belehradek model. The correlation regression suggested that it could describe the influence of temperature on maximum specific growth rate and lag phase to some extent. |
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