| Chilled pork is a representative way of production and consumption and will become the new type of conformation in the fresh pork consumption in the future. However, the growth of contaminated microorganism which lead to the product's spoilage has been become the great barrier for producer during slaughter, transportation and preservation. The problem of meat safty was one of the most important thing that consunmers care of. Presently, the methods of packaging of chilled pork are variety. In order to evluate characteristic index of chilled pork under different package condictions and establish prediction model of microorganisms, this study revealed the quality change of chilled pork during storaging, the best ratio method of gas for modified atmosphere packaging, and the characteristic index of chilled pork under different package condictions, aditionally, with the help of matlab software, we also established and optimized forecast model of microorganism. The contents and results are shown as follows:(1) Based on a series of physiochemical index and microorganisms of chilled pork storaged at 4℃,7℃and 10℃, the result showed that the value of L* at first delined and then rose under the action of water-binding capacity.For the creating and covering of lacitc acid and proteins spliting, the value of pH also delined and then rose,with the same change of the value of shear force and Aw.The value of TVBN rased all the time. The number of staphylococcus kept steady growth in early and mid days, and then with a high-growing rate in the late. The number of pseudomonas growthed rapidly at earlier stage,the low-growing at last showed its growth was inhibited. There was great difference between the number of lactobacillus with and without oxygen which pointed out that the growth rate and position of construction were completely different by different storaging. The number of yeast growthed slowly during 1-7d which showed its growth was inhibited, but it was speeding up during 8-11d, came to the inhibition to some low-temperature bacterium.(2) Chiller pork was analyzed for L*, TVBN, pH value and totel number of microorganisms under pallet, vacuum and modified atmosphere packaging. During 4℃,7℃and 10℃storage, The results showed that the value of L* and pH at first delined and then rose, the value of TVBN and the nunber of microorganisms rose all time,but there were differences between different pakcage condictions.The modified atmosphere packaging (O2:CO2:N2=52:26:22%)showed its dominance as the value was better than those in pallet and vacuum packaging condicition.(3) With the help of Design-Expert 7.0 software, we unified the value L* and shelf life into special index, and then gave each of them a weighting coefficient (0.25, 0.75).The vaule of L* and shelf life multiply by wetghting coefficient and add together into synthetic evaluation value. Analyse the effiction of three kinds of gases to the value L* and shelf life, we obtained that O2 has an important role in keeping a bright-red state to chilled pork, while it came close to 50%, L* value reached 55.9946. High concentration CO2 palyed an important part in effect of antimicrooganisms,but allow for CO2 could make packet contracted, the proportion of CO2 remained 30% was perfect. Based on the theory of parameter assessment, we obtained the logical relation between responses and detection variable by using SLD method. Analysing the experimental data, we obtained the regression equation of synthetic evaluation value of chilled pork during storaging. Y=9.48X1+13.18X2+8.74X3+0.11X1X2-2.95X1X3+5.98X2X3+4.41X1X2X3-41.75X1X2 (X1-X2)+36.98X1X3(X1-X3). On analysis of variance and test of significance in regression equation and regression coefficient, the result showed that regression equation has high-value of F but low-value of P by the same with regression coefficient. The value of R in regression model was 0.9871 showed the model calculation and predication show good agreement with the experimental results.Analysing Contour plot and 3D surface plot, the result showed synthetic evaluation value of chilled pork during storaging were sensitive to to detection variable which have been found to exist by our experiments. Optimizing experimental parameter, by considering the price of this three kinds of gases, the best way of gas proportion was O2:CO2:N2=52:26:22%.(4) Based on Gompertz equation and data of experiment, the microorganisms growth equation have created that was logN=log No+Aexp{-exp[-B(t-M)]}, by help of Matlab software. Being verified by the secondary model and believing degree of testing-data showed the model could precisely describe the growth of microorganisms and was trustworthy and common. At last, prediction model of shelf-life have established, shelf-life(d)={[log(MSL)-log(No)]×1n10}/(U×24)+LPD... |
PDF Full Text Request