| Vibrio parahaemolyticus is gram-negative halophilic bacteria that usually ocuur inwarm marine environment worldwide. It is a kind of common foodborn pathogenicbacteria. After infection in patients with major symptoms is enterogastritis. The data offoodborn diseases were collected and analyzed. Food poisoning that caused by Vibrioparahaemolyticus that already supassed Salmonella leaps to the first. The growth kineticsmodel in breaded shrimp were developed under the different conditions of temperature, pH,NaCl concentration, temperature-pH and temperature-NaCl concentration. We also studiedthe growth rhythm of Vibrio parahaemolyticus in breaded shrimp during fluctuatingtemperature. The Vibrio parahaemolyticus inoculated into shrimp samples were measuredat low temperature, their survival curves were plotted respectively. This paper providestheoretical guidance in the risk assessment of Vibrio parahaemolyticus and perfecting theprocessing techniques of breaded shrimp.The main contents and results are as follows:1. The growth characters of Vibrio parahaemolyticus in shrimp, wrapped in a pulppowder and breaded shrimp were studied in laboratory conditons. And the optimum growthconditons were found out: the optimum temperature of growth was30~37°C, the optimumNaCl concentration of growth was3%~4%, the optimum pH of growth was7.0~8.0.2. To study the growth law of Vibrio parahaemolyticus in the process of breadedshimp, growth curves under different temperatures (10,14,18,22,26,30,37°C,respectively) were determined. The modified Compertz, modified Logistic and Baranyimodels, respectively, were applied to fit the growth curves. The maximum specific growthrates and the lag time, obtained by the optimum growth model, were fitted by theroot-squaring model and the nonlinear model respectively. Results showed that themodified Compertz model was more accurate and useful in fitting Vibrio parahaemolyticusgrowth curves than the modified Logistic and Baranyi&Robert models, respectively(R2=0.9917). And the secondary models of the root-squaring model (R2=0.9687) and thenonlinear model (R2=0.9951) had a high goodness-of-fit. Validation of the models showedthat the predictive models were highly reliable, and can effectively predict the growth ofVibrio parahaemolyticus under above temperature condition.3. To study the growth law of Vibrio parahaemolyticus in the process of breadedshimp, growth curves under different pH (5.5,6,6.5,7,7.5,8,8.5, respectively) were determined. The modified Compertz, modified Logistic and Baranyi models, respectively,were applied to fit the growth curves. The maximum specific growth rates and the lag time,obtained by the optimum growth model, were fitted by the modified Arrhenius model andthe nonlinear model respectively. Results showed that the modified Compertz model wasmore accurate and useful in fitting Vibrio parahaemolyticus growth curves than themodified Logistic and Baranyi models, respectively(R2=0.9938). And the secondarymodels of the modified Arrhenius model (R2=0.9867) and the nonlinear model (R2=0.9487)had a high goodness-of-fit. Validation of the models showed that the predictive modelswere highly reliable, and can effectively predict the growth of Vibrio parahaemolyticusunder above pH condition.4. To study the growth law of Vibrio parahaemolyticus in the process of breadedshimp, growth curves under different NaCl concentration (1%,2%,3%,4%,5%,6%,7%,respectively) were determined. The modified Compertz, modified Logistic and Baranyimodels, respectively, were applied to fit the growth curves. The maximum specific growthrates and the lag time, obtained by the optimum growth model, were fitted by the modifiedArrhenius model and the nonlinear model respectively. Results showed that the modifiedCompertz model was more accurate and useful in fitting Vibrio parahaemolyticus growthcurves than the modified Logistic and Baranyi models, respectively(R2=0.9934). And thesecondary models between the maximum specific growth rates and NaCl concentration(R2=0.9063) had a high goodness-of-fit. So as the secondary models between the lag timeand NaCl concentration (R2=0.9480). Validation of the models showed that the predictivemodels were highly reliable, and can effectively predict the growth of Vibrioparahaemolyticus under above NaCl concentration condition.5. Growth curves of Vibrio parahaemolyticus in breaded shimp under differenttemperature-NaCl concentration (10°C-3%、14°C-6%、18°C-2%、22°C-5%、26°C-1%、30°C-4%、37°C-7%, respectively) were determined. The modified Compertz, modifiedLogistic and Baranyi models, respectively, were applied to fit the growth curves. Toanalysis the effect of temperature and NaCl concentration to the maximum specific growthrates and the lag time, the response surface model was established with stepwise regressionby using JMP7.0software Results showed that the modified Compertz model was moreaccurate and useful in fitting Vibrio parahaemolyticus growth curves than the modifiedLogistic and Baranyi models, respectively(R2=0.9906). And the response surface equationswere m0.02381T0.1726,(R2=0.9664),0.03870T22.285T16.40,(R2=0.9045). The confidences of the models were high by the analysis of variance.6. Growth curves of Vibrio parahaemolyticus in breaded shimp under different temperature-pH (10°C-6.5,14°C-8,18°C-6,22°C-7.5,26°C-5.5,30°C-7,37°C-8.5, respectively) were determined. The modified Compertz, modified Logistic andBaranyi models, respectively, were applied to fit the growth curves. To analysis the effectof temperature and pH to the maximum specific growth rates and the lag time, the responsesurface model was established with stepwise regression by using JMP7.0softwareResults showed that the modified Compertz model was more accurate and useful in fittingVibrio parahaemolyticus growth curves than the modified Logistic and Baranyi models,respectively(R2=0.9921). And the response surface equations are m0.02381T0.1726,(R2=0.9228),0.03870T22.285T16.40,(R2=0.9045). The confidences of themodels are high by the analysis of variance.7. By setting the temperature fluctuations of the Vibrio parahaemolyticus, thetemperature changes in the production and circulation were simulated. According thecomparison between value of prediction and actuality indicated that the precision of model,the values of bias factor and accuracy factor were0.9800~0.9960,1.031~1.043, whichwere accepted statistically. The predictive models were highly reliable. These caneffectively predict the growth of Vibrio parahaemolyticus under above temperaturecondition.8. The variation of inactive Vibrio parahaemolyticus in shrimp under5°C,-4°C and-18°C were studied. Then Linear model, Weibull model and Logistic model were appliedto fit inactive curves of Vibrio parahaemolyticus. Results showed that Logistic model wasproved to be more accurate and useful in fitting Vibrio parahaemolyticus inactivationcurves at low temperature storage based on mathematical evaluation than linear model,Weibulland Linear model.9. Simulation process of the prediction of Vibrio parahaemolyticus in breaded shrimpusing Matlab software was constructed, combined with VC++programming software atthe same time, so a more convenient user interface was created. It provided an importanttool for rapid prediction of Vibrio parahaemolyticus. |
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