The Establishment And Application Of Growth Predictive Model Of Vibrio Parahaemolyticus In Simulated Crab Meat

Vibrio parahaemolyticus is a kind of common pathogenic bacteria causing food poisoning to human, which are widespread in the nature and live in intestines of many kinds of biology, with the highest infection rate of marine organisms in various animals. China takes an important role in processing, import and export of aquatic products. So the detection of Vibrio parahaemolyticus must be inspected as one of the review projects of the import and export of aquatic products in China. How to prevent Vibrio parahaemolyticus in aquatic pollution is a major seafood safety issue.In this thesis, growth predictive models on Vibrio parahaemolyticus in simulated crab meat was studied, and prediction model database was established. A tool of predicting growth dynamics of Vibrio parahaemolyticus in the actual processing or storage conditions for the users was provided, to make simulated crab meat at acceptable levels in the security risk , to play a security role for the simulation of crab meat exports.Main content and results are as follows:1. This thesis studied the growth of Vibrio parahaemolyticus in a different temperature (5℃~50℃), salinity (1.6%~5.2%) on the simulated crab? meat in laboratory conditions, and found out the optimum growth temperature of 30~40℃, and the optimum growth NaCl concentration of 3%~4%.2. The growth law of Vibrio parahaemolyticus in simulated crab meat in the temperature of 4℃, 6℃, 10℃, 12℃, 15℃, 20℃, 25℃, 28℃, 33℃, 37℃were studied by using growth predictive models were established at the fixed temperature conditions. The growth curve of Vibrio parahaemolyticus in the simulated crab meats were fitted with Gompertz and linear equations, and the results showed R2 of the growth curve is above 0.985, and Gompertz and linear model were applied to fit them in the temperature of 4℃~37℃. The secondary growth model of Vibrio parahaemolyticus in simulated crab meat was described by the Belehradek model, whose R2 was 0.9795. The growth curve is typical linear. Validation of the models showed that the residual difference of predicted and observed value was within±0.05, and the values of bias factor and accuracy factor were also acceptable statistically. The predictive models were highly reliable. This provided a reliable theoretical data for the safety of simulatedion crab meat and the quality evaluation, and it can effectively predict the growth of Vibrio parahaemolyticus in the range of 4℃~37℃.?3. The growth law of Vibrio parahaemolyticus in simulated crab meat in the salinity of 2.5%~5.0% were studied by using growth predictive models were established at the fixed salinity conditions. The growth curve of Vibrio parahaemolyticus in 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0% in the simulated crab meats were fitted with Gompertz equations, and the relationship between salinity and growth rate fitted with Ratkowsky3 extended, the results showed R2 of the growth curve is 0.9659. Validation of the models showed that the residual difference of predicted and observed value was within±0.05 (except one in 0.05), and the values of bias factor and accuracy factor were 1.002, 1.1249. They were also accepted statistically. The predictive models are highly reliable. The results show that the effects of the model fitting are satisfactory, with good accuracy, and can predict well the growth of actual product of Vibrio parahaemolyticus.4. Growth curves were fitted in the composite conditions of different temperature- salinity by using Gompertz equation which fits to describe the growth dynamic of Vibrio parahaemolyticus, and obtained growth parameters. The response surface model was established by using Design-Expert software, equations:λ=2.48-0.81T-0.58S+0.20T2+0.15S2+0.009650TS,μ=0.60+0.16T+0.15S-0.027T2- 0.048S2-0.018TS. And the corresponding surface ofλandμwere established through regression analysis to determine with the reliability and acceptability, in order to determine the actual environmental conditions of temperature, salinity and the role and size of its impact.5. By setting the temperature fluctuations of the Vibrio parahaemolyticus in the storage experiment, prediction model for Vibrio parahaemolyticus was established in the temperature fluctuations, and the values of bias factor and accuracy factor were 1.01~1.07, 1.12~1.17, which were accepted statistically. Thereby an effective growth dynamic model of Vibrio parahaemolyticus in simulated crab meat at 4℃~37℃temperature fluctuations was established.6. By measuring the remaining case of Vibrio parahaemolyticus in simulated crab meat s in 60, 70, 80, -5, -18℃, the results were fitted by Logistic models. The inactivation/survival models were established, and the values of bias factor and accuracy factor were within 1.1~1.9, 0.75~1.25 of Vibrio parahaemolyticus. So that the prediction model can predict better, and quantitatively predict the remaining case of Vibrio parahaemolyticus in simulated crab meat.7. Simulation process of the prediction of Vibrio parahaemolyticus in simulated crab meat using Matlab software was constructed, combined with other programming software at the same time, so a more convenient user interface was created, in order to provide better microbial predictive tools for management and research staff. It provided an important tool for rapid prediction of Vibrio parahaemolyticus.