| Chilled pork has been the main form of the fresh pork consumption in a few large or medium cities of our country.However,the growth of microorganism during slaughter,transportation and preservation that lead to the spoilage of product has been the great barrier for producer.And the meat safety was the most attention problem for consumer.By virtue of predictive microbiology models,we can make a quick evaluation for shelf life and quality of chilled pork without traditional test.In the present study,the naturally contaminated chilled pork obtained from the plant A was used as the subject.The chilled pork with pallet and vacuum packaging was examined Pseudomonas,TVBN value and sensory evaluation indicators to determine the spoilage limit of Pseudomonas spp.in chilled pork.The growth law of Pseudomonas in chilled pork was examined at 0,5,10,15,20 and 25°C respectively.The Baranyi,Gompertz and Huang models were used to fit the growth data of Pseudomonas and RSS,MSE,AIC and psedu-R2 were used to comprehensive evaluate the fitting properties of the three models to determine which model better suited to fit the growth data of Pseudomonas obtained directly in chilled pork and could predict the shelf-life of chilled pork in meat production.The results showed that:(1)By comprehensive evaluating the number of Pseudomonas,TVBN value and sensory indictors,the spoilage limit of Pseudomonas spp.in chilled pork under pallet and vacuum packaging are 6.20 log(cfu/g)and 5.33 log(cfu/g)respectively.(2)The nonlinear regression procedure of SAS 9.1 statistical soft ware was used to fit the experimental data of Pseudomonas with three models at different temperatures.At 0°C under vacuum packaging,no growth of Pseudomonas cells was observed,and the number of bacteria actually declined,so the three models could not fit the data.There was a decline of Pseudomonas population during the initial adjustment period of lag phase which is followed by exponential growth at 0-15°C under pallet and vacuum packaging,and the three models cannot fit this special condition accurately.The three models were suitable to describing the growth of Pseudomonas in chilled pork correctly at the other storage temperatures.(3)By comparing the statistical criteria RSS,AIC RSE and psedu-R2 of the three models,the results revealed that the three models gave a different goodness of fit over all the data obtained at selected temperatures.The growth rate and lag phase of which fitted by Gompertz and Baranyi models were determined to established secondary model.And the MSE,RSS and psedu-R2 indicated that the kinetic parameters K and λ fitted by Gompertz model could better describe the influence of temperature on growth finely.The comprehensive analysis of statistical indicators showed that Gompertz model was the most appropriate model to predict the growth of Pseudomonas in chilled pork.(4)Validation of built model was carried out at constant and fluctuating temperatures with the chilled pork obtained from the plant A and B.Bias and accuracy factors and intuitive comparison chart suggested that the development models could finely predict the growth of Pseudomonas in chilled pork from different plants at constant temperature.However,bias factor was within the precise scope and accuracy factor upon the precise scope at fluctuating temperatures.It was difficult to predict the growth of microorganism at fluctuating temperatures,and by the limit of the method,it is still need more study to verify whether the model built at constant temperature could applies to the condition of fluctuating temperatures.(5)The present study provides equations to predict the shelf life of chilled pork under pallet and vacuum packaging provided that the initial number of Pseudomonas organisms(N0)and the actual temperature are known. |
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