| The project focuses on the research of a new natural plant essential oil for chilled fresh chicken meat to prevent bacteria from deteriorating and extend its shelf life.The agar diffusion method was used to test the antibacterial activity of 18 plant essential oils,and Carum copticumessential oils with strongest antibacterial activity and wide antibacterial spectrum against the tested microorganisms such as Escherichia coli,StapHylococcus aureus,Bacillus subtilis,and Salmonella were screened out.Microwave distillation was used to extract the essential oil from Carum copticum seeds and optimize the extraction process by mμLti-target response surface.The resμLts showed that the optimum extraction conditions were as follows:ratio of material to liquid 1:16,extraction time 30 min,microwave power 620 W.The highest extraction rate was 4.48%,the thymol content was 65.78%,and the inhibition zone diameter was 76mm.The main components of Carum copticumessential oil extracted from the Microwave and steam distillation by GC-MS analysis were thymol,which showed no significant differences.Qualitative and quantitative analysis of the main components of essential oil of Carum copticum by Gas ChromatograpHy-Mass Spectrometry(GC-MS)showed that the main inhibitory components of essential oil of Carum copticum were thymol,gamma-terpinene,and p-umbelliferon.The relative content of and thymol was 60.36%,and its absolute content was 0.268 g/mL.The minimum inhibitory concentrations(MIC)of Carum copticum essential oils of E.coli,S.aureus,Salmonella and B.subtilis were determined to be 0.4,0.125,0.25,and 0.4μL/mL,respectively;the minimum bactericidal concentrations(MBC)were 0.8,0.5,0.5,and 0.8μL/mLrespectively,Using electron microscopy,intracellμLar nucleic acid,protein content,potassium ion and other techniques,the inhibition mechanism of different concentrations of essential oil of Carum copticum on Escherichia coli and StapHylococcus aureus was studied.The resμLts showed that the antibacterial action of essential oil of Carum copticum on Escherichia coli and StapHylococcus aureus was to destroy its cell membrane structure,resμLting in a large number of metal ions,such as proteins and potassium ions,in microbial cells.Disintegration of the spiral structure.To investigate the effect of the concentration of essential oils of Carum copticum(0.4,0.6,0.8,and 1.0 μL oil/g chicken)on the fresh-keeping effect of chilled chicken under refrigeration conditions(4℃)and the volatilization rate of essential oil of Carum copticum in package bags.Comparing the indexes of volatile base nitrogen,total bacterial count,pH value,TBARS value,and sensory quality of the chicken during storage,it was found that Carum copticum essential oil quickly evaporates in the packaging bag to form a bacteriostatic atmospHere.When the concentration of essential oil in chilled chicken packaging bag was 0.6μL/g and 0.8μL/g respectively,the peak area reached the maximum after 24h,and the gas falling rate in the bag with large concentration of essential oil was slower than the concentration,double the shelf life of chilled chicken(12 days)(based on volatile base nitrogen),extend the shelf life of chilled chicken by 9 days(1.5 times)at an essential oil concentration of 1 μL/g.The effect of the position of Carum copticum essential oil in the packaging(100 μL:chicken 100 g)on the fresh-keeping of the chilled chicken and the volatilization rate of the essential oil in the bag was measured.The resμLts showed that the peak area reached at the 24th hour.The maximal area of the thymol peaks in the U-L group(upper chicken layer),UL-L group(lower chicken layer),and L-L group(lower chicken layer)in the liner positions were 2.04×109,1.82×109,1.22×109,respectively.Gas bags have the fastest rate of gas concentration drop;individual essential oil liners are placed on the upper or lower layers of the chicken to extend the shelf life of chilled chickens to 15 days compared to the control group(5-6 days),while the two essential oils are cushioned SimμLtaneously placed in the lower and upper layers of the chicken,the shelf life of chilled chickens was extended to 18 days. |
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