Establishment Of Predictive Models For Salmonella In Pasteurized Liquid Whole Egg

Salmonella is a kind of food born pathogen that often causes human diseases.They are widespread in the nature. In kinds of food, egg products hold the highest detection rate of Salmonella.. China is the egg-producing country in the world.The production of egg products occupy a certain proportion.Salmonella contamination has seriously affected the quality and superiority of egg products in our country. In this paper, the growth characteristics of Salmonella were studied and establishing primary and secondary models in pasteurized liquid whole egg. The purpose is that we can predict Bacteria number changes of Salmonella quickly and accurately and take certain preventive measures timely, avoidimg risks and eliminating hazards.Seventeen strains of suspicious microorganisms were separated from eggs sold in market. After isolation and identification,two of them were identified as Salmonella and serotypes were O. Salmonella,No. 1.1552,was bought from Institute of Microbiology Chinese Academy of Sciences.Its growth in pasteurized liquid whole egg was similaer with the strain separated from eggd.So,the one we bought was treated as the object of study of predictive models.Growth characteristics of Salmonella were studied in pasteurized liquid whole egg and nutrient borth and the optimum growth temperature, pH value and NaCl concentration were ascertained.We can choose Gompertz ,Richards and Logistic models to fit growth data of Salmonella at 4℃,7℃,12℃,20℃,25℃,30℃and 37℃.All of temperatures were able to fit S-shaped curves well except 4℃. After contrasting of coefficient correlation and standard error and comparison of model parameter meaning and model complexity, final decision was to use Modified Gompertz model fit growth data of Salmonella at different temperatures, establishing primary model. All correlation coefficients were above 0.99, high fitting degree.According to meaningful parameter values obtained from primary models under different temperatures, secondary models were established about the square root of growth rate and temperature, the reciprocal square root of lag phase and temperature. The correlation coefficient of these two models were above 0.98.We can predict growth rate and lag phase under different temperatures by square root models and understand growth of Salmonella.Comparing growth data of Salmonella in pasteurized liquid whole egg with liquid whole egg at 4℃,12℃and25℃,taking significant analysis,P all above 0.05,shows that there was no significant difference of growth of Salmonella in two nutrition matrixes. The growth predictive model of Salmonella can be applied in liquid whole egg as well as pasteurized liquid whole egg. In the application of the model,we have established growth dynamic model of Salmonella in liquid egg according to primary model and concrete secondary models. Making sure the initial bacterial count, we can calculate the bacterial count at any time and temperatures.It substitutes the growth dynamic model with minimum response dose 105cfu/ml of Salmonella poisoning.After clearing up,we got an equation of time about t.In other words ,it is shelflife predictive model.We validated models in this research.the results were that prediction of growth rate and lag phase for Salmonella in pasteurized liquid whole egg were confirmed and shelflife was reliable.The application extension of predictive model was enlarged.