Isolation, Identification Primary Spoilage Bacterium From Non-ferment Soy Product And Preservative Studies

This experiment, using non-ferment soy product for its material, gained four sort of spoilage bacterium: df1, df2, df3, df4 through separation and purification in the spoiling process of non-ferment soy product. In the experiment it carried out systematical research on the properties of configuration, bacterial community and the physiological and biochemical properties. It can be concluded from the final identification that the four leading spoilage bacterium which led to the spoilage of soy product were: E.agglomerans, B.pumilus, B.megaterium.and S.caseolyticus.The result of testing roles of paraben, potassium sorbate, compound preservatives and natural propolis in inhibiting the four leading spoilage bacterium indicates: Paraben failed to inhibit all the four leading spoilage bacterium at its maximum dosage-1 percent according to international discipline, so did potassium sorbate; Compound preservatives can inhibit df1, df3, df4,but not df2; While propolis can inhibit the four leading spoilage bacterium at a dosage of 0.04 percent. So what was most available in this experiment was: propolis.Having tested the growth conditions of the four leading spoilage bacterium and compared the growth curves among them, so concluded that propolis inhibited the four leading spoilage bacterium mainly in their growth in delay and logarithm periods so as to inhibit the growth of the number of bacteria .The total number of bacterial community, the pH in effect and the percentage of volatilization brine nitrogen were applied to measure the antisepsis effect of non-ferment soy product. The total number of bacterial community on the non -ferment soy product changd from 5.7x104cfu/ml at the beginning to 4.8x109cfu/ml after 30-days' storage and the pH rose, fell, then rose, from 6.71 to 7.10 in the long run. the percentage of volatilization brine nitrogen also rose from 4.93mg/100g to 182.96mg/100g. A crossed experiment was also designed with regard to factors affecting it: the concentration of propolis, the packaging mode and the storage temperature, which was carried out to measure the effect of non-ferment soy product in whole process in term of the percentage of volitilization brine nitrogen. The result indicates that the most suitable combination to prolong the time limit of storage non-ferment soy product were: 0.4%opropolis + 0.02x105Pa vacuum packaging +storaging temperature under 4C,which cart prolong the shelf life to 35-days,making the total number of bacterial cornmuity reached 9.3X 104cfu/ml,pH 6.56 and the percentage of volatilization butyl nitrogen 22.00mg/100g,there was no difference between blank and sample.