| Chilled mutton which had high nutritional value was healthy and safe,but meat was easily contaminated by microbial,and the shelf life was short.Therefore,the development of chilled mutton preservation technology was of great significance.In this experiment,Euler Tibetan sheep was used as raw material,and cumin,pepper and cinnamon essential oil were used as bacteriostatic agents.Double-layer agar diffusion method was used to test the MIC values of the seven kinds of bacteria.On the basis of this,the compound antibacterial formula of natural preservative was determined by orthogonal test.Comprehensive application of physicochemical and other indicators to evaluate the preservation effects of compound natural preservative.The effects of compound preservative on the main endogenous proteases and antioxidant enzymes of chilled mutton were studied.The results were as follows:1.The antimicrobial activity of the three essential oils were determined by double-layer agar diffusion method as follows: When the concentrations of cumin,pepper and cinnamon essential oil were 0.80%,0.70% and 0.50%,respectively,they had inhibitory effects on 7 main putrid bacteria and pathogenic bacteria in chilled mutton.Considering the diffusion effection of preservative in meat and the change of TVB-N in the pre-experiment,the optimal compounding formula of natural preservative was determined as: the concentration of essential oil of cumin,pepper and cinnamon were 12.8%,5.6% and 4.0% respectively.2.The effect of compound preservative on chilled mutton(1)The effect of compound preservative on physical and chemical indexes of chilled mutton: The L* and a* values of the chilled mutton treated with compound preservative were higher than those of the control and blank groups during the whole preservation process.The shear force value was significantly higher from 4 day than the control and blank groups(p<0.05).Water content and b* value were lower than control and blank groups.The total number of colonies,cooking loss rate,TBA and MFI values were significantly lower from 4 day than the control and blank groups(p<0.05).The pH and centrifugal loss rate were significantly lower from 8 day than the control and blank groups(p<0.05).Compound preservative treatment would improve the physical and chemical indexes of chilled mutton,and the preservative period was extended from 8 days to 16 days.(2)The effect of compound preservative on the activity of endogenous protease in chilled mutton: The Cathepsin-B and D of chilled mutton treated with complex preservative were significantly lower than the control and blank groups(p<0.05)from 4 days,Cathepsin-L was significantly lower than the control and blank groups(p<0.05)on 4 days,?-calpain was significantly higher than the control and blank groups(p<0.05).In the treatment group,the Cathepsin-B was 7.45% lower than that of the blank group and 7.67% lower than that of the control group at 4 days,Cathepsin-D was 12.07% lower than the blank group and 8.87% lower than the control group,Cathepsin-L was 8.46% lower than the blank group and 5.36% lower than the control group,and ?-calpain was 15.21% and 12.83% higher than the blank and control groups.The treatment of compound preservative had certain influence on the endogenous protease of chilled mutton.(3)The effect of compound preservative on main antioxidant enzymes of chilled mutton: CAT,POD and SOD activities of chilled mutton treated with compound preservative were significantly higher than those of control and blank groups(p<0.05)from 4 days.The CAT activity at 4 days was 22.82% and 21.61% higher than that of blank and control groups,respectively.The POD activity at 4 days was 17.31% and 18.92% higher than that of blank and control groups,respectively,and the SOD activity was 40.13% and 29.83% higher than that of blank and control groups,respectively.The application of essential oil would maintain the activity of CAT,POD and SOD and delay senescence.3.Correlation analysis:(1)Correlation analysis of endogenous protease and tenderness: Lysosomal cathepsin was positively correlated with shear force and negatively correlated with MFI.?-calpain was significantly correlated with shear force and MFI(p<0.01).(2)Correlation analysis of major antioxidant enzymes with fat oxidation and protein oxidation: The major antioxidant enzymes in the blank and control groups were negatively correlated with TBA(p<0.05).In the treatment group,TBA was negatively correlated with CAT and SOD(p<0.01),and was negatively correlated with POD(p<0.05).TVB-N was negatively correlated with POD and SOD(p<0.05),and was negatively correlated with CAT(p<0.01).The compound essential oil would slow down the activity of main antioxidant enzymes.In summary,essential oils of cumin,pepper and cinnamon had inhibitory effects on 7 main spoilage bacteria and pathogenic bacteria in chilled mutton.After the combination of 12.8% cumin,5.6% pepper and 4.0% cinnamon essential oil on chilled mutton,the preservation effect would be improved and the preservation time would be extended for 8 days. |
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