Study On Germicidal Effect And Mechanism Of HVPEF Combined With Cinnamaldehyde Treatment On Listeria Monocytogenes

Listeria monocytogenes is a foodborne pathogen,which widely exists in meat products,aquatic products,soybean products and other food.It can cause zoonotic listeriosis after infection,which is extremely harmful.At present,there are many methods for the sterilization of the bacteria,including hot sterilization technology and non-hot sterilization technology.Thermal sterilization technology is widely used at present,but it will affect the nutritional composition or quality of food itself,which does not meet people's pursuit of high-quality food.Therefore,in recent years,non-thermal sterilization technology such as natural antibacterial agent,high pressure burr electric field technology and so on,can well solve the problems brought by the traditional sterilization method,and gradually become one of the research hot spots in the field of food safety.Listeria monocytogenes was used as the main research object in this experiment,through the different intensity of HVPEF at the same time,the view of high voltage electric field of single prick Listeria monocytogenes effect,the effects of combination of cell membranes and DNA analysis,further interpretation of the HVPEF of single prick increases the bactericidal mechanism of Listeria monocytogenes.In addition,the sterilization effect of HVPEF combined with cinnamaldehyde and its application in food were studied.The specific research contents and results were as follows:(1)The bactericidal effect of HVPEF on Listeria monocytogenes in 0.9%and 3%Na Cl solution was slightly worse,and the bactericidal effect in 3%Na Cl solution was higher than that in 0.9%/Na Cl solution.The bactericidal effect on plate surface was the best,reaching 97.48%±2.18%.HVPEF is more suitable for bactericidal application of Listeria monocytogenes in solid matrix.(2)The effects of HVPEF treatment on the inactivation of Listeria monocytogenes were studied.With the extension of sterilization time,the germicidal effect of HVPEF increased continuously,and basically reached equilibrium after 12min.And in the sterilization time of 9 min,with the increase of the concentration of bacteria,the sterilization effect has a significant impact,the lower the concentration of bacteria,the better the sterilization effect.(3)HVPEF treatment resulted in the leakage of nucleic acid,protein and other macromolecules and K⁺outflow in Listeria monocytogenes cells.The decrease of DNA in L.monocytogenes cells before and after HVPEF treatment was detected by FLOW cytometry with AO staining.HVPEF treatment resulted in DNA degradation.PI staining of Listeria monocytogenes cells before and after high pressure barb electric field treatment increased the number of stained cells and the fluorescence intensity increased with the increase of treatment time(P<0.05),indicating that high pressure barb electric field treatment caused damage to the cell membrane of Listeria monocytogenes.Fluorescence staining showed that,with the increase of HVPEF treatment time,the intracellular ROS of L.monocytogenes gradually accumulated,indicating that HVPEF treatment can break the intracellular ROS balance of bacteria,which may be one of the reasons why HVPEF plays a bactericidal role.(4)The combination of HVPEF and cinnamaldehyde could improve the sterilization effect.HVPEF combined with cinnamaldehyde treatment accelerated the outflow of nucleic acids and proteins in Listeria monocytogenes.It causes degradation of DNA,and the damage of cell membrane was aggravated.(5)The germicidal effects of HVPEF treatment and combination of HVPEF and cinnamaldehyde in different concentrations on beef and dried tofu were studied.The results showed that the germicidal effect was related to the roughness of food surface,and the food with rough surface had poor germicidal effect.When the electric field conditions remain unchanged,the germicidal effect increases with the increase of cinnamaldehyde treatment time.The higher concentration of cinnamaldehyde,the better the bactericidal effect.,the better the sterilization.After the treatment of HVPEF(14 k V and 15 min),the sterilization rates were 51.16±2.34%(beef)and62.33±2.77%(dried tofu).Food treated with HVPEF combined with 1/8 MIC and 1/4MIC cinnamaldehyde was placed in refrigerator for 12 h and 24h.With the increased of the storage time,the mortality of L.monocytogenes was increased.When HVPEF combined with 1/4 MIC cinnamaldehyde was placed in refrigerator for 24h,the sterilization rates were 82.21±0.41%(dried tofu)and 65.32±3.46%(beef).To sum up,this paper described the germicidal mechanism and germicidal effect of HVPEF combined with cinnamaldehyde,providing an efficient,green and energy-saving sterilization method for food industry germicidal treatment.