| Because of lettuce is rich in nutrients and good taste, many consumers like it.But,it is also lead to the outflow of nutrients as a result of destruction of the integrity of the original fruits and vegetables.And,it provide extremely favorable conditions for the growth and reproduction of the spoilage organisms and pathogenic microorganisms, serious threat the food safety of the consumer and the quality of product in shelf Life.In order to predict the microbial growth dynamics in fresh-cut product better, The experiment use the fresh-cut lettuce as the case study, fitting the growth curve of the Salmonella. The main contents and conclusions as follows:1、through laboratory-made fresh-cut lettuce after inoculation salmonella at 4℃, 10℃,20℃ and 36℃ four different temperature storage, Growth curves of four Salmonella drawing temperature. Respectively, using a modified Gompertz model, MMF model, Logistic model and Gompertz model uncorrected for Salmonella growth curves were four temperature level model fitting. Using standard deviation r and correlation coefficient s fitting model for evaluation. The evaluation results of the fitting:Under 10℃, 20℃ and 36℃ storage conditions of fresh-cut lettuce salmonella growth curve to correct the Gompertz model fits best; Quadratic curve fitting using the best survival at 4℃.2、To the square root of the model as a basis, substituting the modified Gompertz Growth model fitting parameters, Create a predictive model representation of temperature on the secondary growth parameters influence. By residual analysis, accuracy factor (AF) and bias factor (BF) to test the model. The results showed that the residuals between±0.05, exact factor of 1.0339, deviation factor of 1.0055, indicating that this model is more accurate and can be used in fresh-cut lettuce salmonella maximum specific growth rate forecast the impact of temperature on.3、With storage temperature, the amount of tieback salmonella bacteria, the wound caused by segmentation, fungicide concentration factor as each single factor test, to establish a single factor under different levels of Salmonella growth curves, the latter using the modified Gompertz model to calculate the maximum the specific growth rate (U/h-1) and the delayed phase (LPD/h), the filter parameters for Growth Salmonella a relatively large three groups of factors, The results is:storage temperature, the amo unt of inoculation salmonella bacteria, the wound caused by segmentation are significant factors.The level of the storage temperature is 4℃,10℃,20℃ and 36℃； the level of the Salmonella bacteria inoculation amount is 1 X 103cfu/g,1 × 104cfu/g and 1 × 105cfu/g; wound area caused segmentation experimental level as 1cm,3cm and 5cm.4、Three groups of factors were selected response surface design and testing, Using the modified Gompertz growth curve model fitting, The maximum specific growth rate parameters as secondary response prediction model building. Survival model which appears a "mirror image" of the survival curve into a growth curve fitting and then. The results show that the temperature and the amount of tieback salmonella bacteria Salmonella in fresh-cut lettuce significantly affect (P<0.01), wound area segmentation caused by salmonella on fresh-cut lettuce was significantly affected (0.01<P<0.05). And the temperature and the amount of bacteria tieback interaction obvious, but the wounds caused by splitting its impact is only a linear relationship.5、Through internal and external model checking, using the mean square error (MSE), the deviation factor (BF) and accuracy factor (AF) for the two models were tested. The results showed that internal inspection MSE= 67.7 × 10-4, BF= 0.9281, AF= 1.1504, external inspection MSE= 60.8 ×10-4, BF= 1.1501, AF= 1.2163, description model in an acceptable range, you can simulate Growth of Salmonella in fresh-cut lettuce in a survival situation. |
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