Study On The Inhibitory Mechanism Of Ozone On Spoilage Molds Of Fresh-peeled Garlic

Fresh-peeled garlic has the advantages of convenience and rapidity in eating,which is in line with the fast-paced life style.However,fresh-peeled garlic is prone to deterioration in quality such as yellowing,rooting,germination and mildew during storage,which greatly reduces its economic value.In this paper,aimed to the problem,the spoilage molds of fresh-peeled garlic were isolated and identified.Then,the ozone as antimicrobial agent to study the bacteriostatic effect of different ozone conditions on spoilage molds of fresh garlic in vitro and vivo,and to optimize the ozone treatment conditions.Next,the optimum ozone conditions were used to treat spoilage molds,respectively.Transcriptome sequencing and gene differential analysis of spoilage molds treated and not treated with ozone were carried out,which provided theoretical reference for the mechanism of ozone inhibiting spoilage molds of fresh-peeled garlic.(1)Four strains of spoilage molds from fresh-peeled garlic were separated and purified by plate marking method.Through morphological characterization,mycelial microscopic observation and molecular biology analysis,four strains of spoilage fungi were identified accurately: Penicillium citrinum strain,Rhizopus stolonifer strain,Gibberella intermedia strain,Aspergillus ochraceus strain.(2)In vitro,different ozone concentration,time,temperature and humidity were used to treat spoilage molds of fresh-peeled garlic,respectively.The results showed that ozone treatment could effectively inhibit the mycelial growth of four spoilage molds,change the morphology spoilage molds,destroy the integrity of cell membranes,and cause the outflow of proteins,polysaccharides and other substances in cells,resulting in the increase of the conductivity of bacterial suspension and its death.In conclusion,when the ozone concentration was 6-8 ppm,the treatment time was 15-20 min,the treatment temperature was20-25 °C and the treatment humidity was 90%,the spoilage molds of fresh-peeled garlic could be inhibited in vitro.(3)In vivo,the antibacterial conditions of ozone were further optimized.Fresh-peeled garlic inoculated with P.citrinum,R.stolonifer,G.intermedia and A.ochraceus was treated with ozone under different conditions,respectively.The results showed that ozone concentration,treatment time and humidity had significant effects on the indexes of fresh-peeled garlic,while ozone treatment temperature had no significant effect.The optimum ozone treatment conditions for fresh-peeled garlic inoculated with four kinds of spoilage molds were ozone concentration of 6 ppm,time of 15 min,temperature of 20°C and humidity of 90%.After ozone treatment,the total number of colonies,fungi and yeast,incidence,lesion seize and depth of fresh-peeled garlic can be significantly reduced during storage,and better bactericidal inhibition effect can be achieved.(4)P.citrinum,R.stolonifer,G.intermedia and A.ochraceus were treated with the ozone treatment conditions(concentration of 6 ppm,time of 15 min,temperature of 20°C,humidity of 90%).The RNA-sequencing and gene expression differential analysis were carried out for spoilage molds treated and not treated with ozone.When ozone inhibited the growth of P.citrinum,1531 differentially expressed genes were screened,including 922 genes up-and 610 genes down-regulated,which affected cell,catalytic activity,biological regulation,amino acid metabolism and carbohydrate metabolism.When ozone inhibited the growth of R.stolonifer,970 differentially expressed genes were screened,including 546 genes up-and 424 genes down-regulated,which affected cell,catalytic activity,binding process,carbohydrate metabolism,amino acid metabolism and translation process.When ozone inhibited the growth of G.intermedia,2754 differentially expressed genes were screened,including 1456 genes up-and 1298 genes down-regulated,which affected the pathways of catalytic activity,binding transport activity,cell process,amino acid metabolism,carbohydrate metabolism and lipid metabolism.When ozone inhibited the growth of A.ochraceus,2378 differentially expressed genes were screened,including 1591 genes up-and 787 genes down-regulated,which affected the pathways of cell,organelle part,catalytic activity,binding process,amino acid metabolism,global and overview maps,lipid metabolism and so on.