Effect Of Different Packaging On The Dominant Spoilage Bacteria And Shelf-life Prediction Model Of Chilled Meat

Chilled meat has always maintained at 0⁴? in the course of processing,circulation and sales.Microbial growth and reproduction is inhibited to a certain extent.But the cold chain of meat is still in the initial stage in China at present,a series of conditions offten appear in the logistics process of chilled meat,such as cold chain breakage and the temperature fluctuations.Chilled meat is mainly exposed to the air in the logistics process,and vulnerable to secondary pollution,and the time-consuming and labor-consuming index detection methods bring out the result hysteresis.Chilled meat is a pretty microbial breeding matrix because of its rich nutrient and high water content.As a result,chilled meat is easy to rot and shelf-life is short.In this paper,the effects of different packaging methods and different gas ratio on the chilled pork were studied.The best packaging method and gas ratio were determined.The shelf life prediction model of chilled pork treated with modified atmosphere packaging and composite biological preservative was established.The main results are as follows:1.By monitoring the changes of O₂ and CO₂ content in the modified atmosphere packaging,the PE/PA composite packaging bag?110mm×150mm×0.19mm?with high gas resistance was selected as the material of vacuum and modified atmosphere packaging.2.The quality and shelf life of chilled pork with different packaging was different during the storage at 4?.The shelf life of no packaging and pallet packaging was not more than 4d,that of the modified atmosphere packaging group with high oxygen content?80%O₂+20%CO₂?is 6d,and that of the vacuum packaging group and modified atmosphere packaging group with low oxygen content?35%O₂+65%CO₂?is 9d.Vacuum and modified atmosphere packaging were conducive to extend the shelf life of chilled pork,but the vacuum packaging made the meat dark red,affecting the sensory quality.Therefore,the best packaging method of chilled pork at 4? is low oxygen packaging,that is 35%O₂+65%CO₂.3.Four different gas ratios of modified atmosphere packaging?35%O₂+65%CO₂,55%O₂+45%CO₂,15%O₂+80%CO₂+5%N2 and 35%O₂+55%CO₂+10%N2?were used for chilled pork stored at 4?.According to the microbial indexes of chilled pork during storage?total bacteria,Pseudomonas,Brochothrix thermosphacta,lactic acid bacteria,Lactobacillus and Enterobacter bacteria?and the changes of TVB-N value and MDA value,we obtained the optimal gas proportion.Modified atmosphere packaging?35%O₂+65%CO₂?could inhibit thegrowth of spoilage bacteria,slow down the lipid oxidation,prolong the shelf life of chilled pork,and the preservation effect was the best.4.During storage,the content of O₂ decreased and the content of CO₂ increased in the modified atmosphere packaging.The content of O₂ was positively correlated with the dominant spoilage bacteria,and the content of CO₂ was negatively correlated with it.The correlation and significance varied with O₂ and CO₂ ratios.The effects of O₂ and CO₂ on the dominant bacteria were analyzed by the multiple regression method,and the fitting equation was established in the best modified atmosphere group?35%O₂+65%CO₂?.The regression equations of the effect on Pseudomonas,total bacteria and Brochothrix thermosphacta of O₂ and CO₂ content fit well.The regression equations were: Y=9.580-0.0093X1+0.10X2,R2=0.92?P<0.01?;Y=8.032-0.0067X1+0.75X2,R2=0.90(P<0.01;Y=2.1690.067X1+0.079X2,R2=0.84?P<0.01?,where X1 is the the value of O₂ content,and X2 is CO₂.5.The growth curves of the total number of colony of chilled pork treated with modified atmosphere packaging?35%O₂+65%CO₂?were studied.The dynamic models of the total number of colonies were well fitted by the modified Gompertz equation,and R2 was more than 0.95.The shelf life prediction model?SL?was established,and the model parameters were: b?=0.016,Tmin?=-36.8012,b?=0.013,Tmin?=-50.715,Nmax=7.0933 lg?cfu/g?,N0=3.0340lg?cfu/g?.The accuracy of the predicted model?SL?was verified by comparing the measured values of the total number of colonies with the predicted values of chilled pork at 4?.The results showed that the relative error between the measured value and the predicted value was-4.28%,which indicated that the prediction model?SL?could be used to predict the shelf life of chilled pork treated with modified atmosphere packaging.