Study On The Inhibitory Mechanism And Application Of High Voltage Electric Field On Salmonella Enteritidis

Salmonella enteritidis(S.enteritidis)is typical foodborne pathogenic bacteria that can cause zoonosis.It is extremely harmful.The vast majority of Salmonella infections are transmitted through the food chain.S.enteritidis is widely found in fruits and vegetables,aquatic products,dairy products,meat products and other foods.Therefore,it is of great significance to apply sterilization technology to inhibit S.enteritidis pollution for food safety.Thermal sterilization technology is a conventional sterilization method to kill microorganisms in food.However,high temperature may seriously affect the color,taste and nutritional quality of food itself.As a non-thermal sterilization technology,high voltage electric field sterilization has attracted much attention because of its advantages such as small nutrition damage,small flavor,color,small temperature change,and environmental protection.Taking S.enteritidis as the research object,this paper first screened the germicidal efficacy of S.enteritidis under different types and different voltage intensities of electric field treatment,then combined with the integrity of S.enteritidis out membrane and the analysis of oxidative stress damage,elaborated the germicidal mechanism of high voltage prick electric field(HVPEF).Finally,by applying electric field treatment to the surface of salmon,chicken breast,steak,and sausage slices,the sterilization effect in food was explored,and the sensory quality changes of chicken breast during storage were further explored.The research contents and conclusions of the full text are as follows:(1)Taking S.enteritidis in different physiological environments as the research object,the sterilization evaluation of different types and different voltage electric field treatment was explored.The results showed that the HVPEF had the most significant bactericidal effect on S.enteritidis on the surface of solid substrate,and the bactericidal rate of S.enteritidis reached more than 95% when treated with 13 k V voltage for 15 min.In contrast,the sterilization effect of electric field treatment on S.enteritidis in liquid environment is poor,and the concentration of Na Cl has a significant impact on the sterilization effect of electric field.(2)The inactivation kinetics of S.enteritidis on solid surface treated by HVPEF was studied.The results showed that the survival rate of S.enteritidis decreased with the prolongation of sterilization time when the HVPEF intensity was 13 k V;At the same time,the sterilization efficiency of electric field is closely related to the initial colony density of S.enteritidis.The smaller the initial colony density,the shorter the sterilization time of HVPEF,and the stronger the inactivation effect.(3)Under the treatment of HVPEF,the leakage of intracellular substances,permeability of outer membrane,fluidity and changes of cell morphology of S.enteritidis were analyzed,and the mechanism of prick electric field on cell out membrane integrity damage was studied.To analyze the ROS(reactive oxygen species)accumulation,MDA(malondialdehyde)production and DNA structure changes of S.enteritidis,and study the oxidative stress damage mechanism of S.enteritidis treated by HVPEF.The results showed that HVPEF treatment led to the leakage of proteins and nucleic acids in the cells of S.enteritidis,which indicated that the electric field treatment destroyed the permeability of the cell membrane.The results of fluorescence staining showed that the treatment of HVPEF affected the outer membrane permeability and fluidity of S.enteritidis.With the increase of electric field treatment time,the outer membrane permeability of the bacteria gradually increased,and the membrane fluidity gradually decreased.The SEM results showed that the treatment of HVPEF led to the loss of normal morphology of cells,holes in the cell membrane,a large amount of intracellular substances overflowed,and the damage of the integrity of the cell membrane was aggravated.The treatment of HVPEF aggravated the accumulation of ROS in cells,caused membrane lipid peroxidation,and led to a significant increase in MDA level,indicated that S.enteritidis had an oxidative stress effect on the application of electric field.The results of AO staining showed that the treatment of HVPEF led to the degradation of DNA and destroyed the complete structure of DNA.(4)Taking salmon,chicken breast,steak and sausage slices as food research objects,the sterilization effect of HVPEF applied to food surface was investigated.By measuring the changes of total bacterial count,color difference,texture,p H value,volatile basic nitrogen(TVB-N)and thiobarbituric acid(TBARS)during storage,the effect of HVPEF treatment on the sensory quality of chicken breast meat was explored.The results showed that the prick electric field had the most significant sterilization effect on S.enteritidis on the surface of salmon and chicken breast,especially when treated at 14 k V for 30 min,the sterilization rate of salmon and chicken breast reached91 ± 1.6% and 88.2 ± 2.2% respectively.The results of chicken breast meat quality indicators indicated that the change of color difference and texture of chicken breast was not significant;The change of total bacterial count and p H value of chicken breast meat after electric field treatment was significantly lower than that of the untreated group.Moreover,the content of TVB-N and TBARS in chicken breast meat was significantly decreased,indicated that electric field treatment protected the original quality of food to a certain extent and delayed the decay of food.