| Chlorine dioxide is a class A1 safe and highly effective fungicide confirmed by the World Health Organization and the U.S.Food and Drug Administration,and does not produce harmful substances such as chloroform after reacting with organic matter;it is widely used in fruit and vegetable preservation,fish and meat processing and other fields because of its wide applicability,low dosage,fast reaction,good effect and long duration.Monilinia fructicola caused by brown rot bacteria is the most destructive disease of peaches after harvest,which is very easy to lead to peach rot and deterioration,causing huge economic losses.The bactericidal effect of chlorine dioxide on bacteria cultured in liquid has been reported in the literature,while the bactericidal activity of chlorine dioxide on bacteria in solid state has rarely been studied.In this paper,the actual situation of fruit storage process was simulated,and the bacteria were cultured in the solid state by the inversion method of bacterial cake to investigate the bactericidal effect and inhibition mechanism of chlorine dioxide on Monilinia fructicola,Yeast and E coli.The results showed that the colony diameters of Monilinia fructicola were significantly smaller than those of Yeast and E.coli after the same concentration of chlorine dioxide treatment;chlorine dioxide had different degrees of damage to the cell membranes of Monilinia fructicola,Yeast and E.coli,and the higher the concentration of chlorine dioxide,the greater the cell membrane damage;the extracellular protein content of brown rot bacteria increased significantly after chlorine dioxide treatment,which was 3.1 times that of the blank group,and the same treatment of The protein content of Saccharomyces cerevisiae and Escherichia coli increased by 68.84% and 59.31%,respectively,compared with the blank group;with the increase of chlorine dioxide concentration,the extracellular DNA content of bacteria increased rapidly and the dehydrogenase activity decreased rapidly;the results of scanning electron microscopy after chlorine dioxide treatment of the three bacteria revealed multiple agglomerates and exudates,and the morphology of some parts of bacteria changed,with dry and rough surface,depression,damaged cell membrane and boundary blurred.The bactericidal effects of chlorine dioxide and UV were compared.The results showed that the colony diameters of the chlorine dioxide group were smaller than those of the UV group after the same treatment time,and the colony diameters of Monilinia fructicola、Yeast and E coli decreased by 7.63,5.13 and 4.51 cm,respectively,after 4 h of chlorine dioxide treatment compared with the blank group.chlorine dioxide and UV treatment could damage the cell membranes of the three strains,and the degree of cell membrane damage increased with the increase of treatment time.The protein content of brown rot bacteria increased by0.041 and 0.039 mg/m L after chlorine dioxide and UV treatment,respectively,compared with the blank group.the DNA content was higher after chlorine dioxide treatment than UV treatment at most time effects,and the longer the treatment time,the higher the MDA content and lower the dehydrogenase activity of the three strains;the status of the three strains changed from live cells to early apoptosis after chlorine dioxide and UV treatment and late apoptosis,the percentage of early apoptosis of Monilinia fructicola,Yeast and E.coli were56.72%,58.22% and 57.16%,respectively,and the scanning electron microscope results found that the morphology of the bacteria changed,the surface was concave and there was exudate.In this paper,tartrate was prepared as w/o/w emulsion with citric oil as oil phase,and then dispersed in sodium alginate gel matrix to form w/o/w compound emulsion,and the tartaric acid diffused into the external aqueous phase reacted with sodium chlorite therein to release chlorine dioxide slowly.In this paper,the preparation conditions of emulsion oil phase,emulsifier and external aqueous phase gel matrix were screened,and the gel retarder sodium chlorite residue was produced with the relationship equation of time,which can be released continuously for more than 20 d under high temperature above 30 ℃ in summer,playing an important role in extending the shelf life of fruits and vegetables.The developed chlorine dioxide gel retardant was used for the preservation of Longquan peach,and the manufactured gel was placed in the fruit box of peach as a whole(A),cut into2 pieces(B)or 3 pieces(C),and the peach was taken out every 2 d to examine the Mukuan index for 10 d.The results showed that the titratable acid content of peach in the blank control,A,B and C groups decreased by 31.33%,29.5%,28.32% and 26.82%%;soluble solids increased by 2.54%,2.15%,1.72% and 0.92%,respectively;mass loss rate was 4.06%,3.68%,3.75% and 3.24%,respectively;decay index was 0.55,0.5,0.47 and 0.43,respectively;hardness decreased by 45.77%,40.75%,35.32% and 30.85%,respectively.35.32% and30.85% respectively;relative conductivity increased by 50.6%,43.56%,38.8% and 36.5%respectively;MDA content increased by 3.17,2.81,2.5 and 2.42 nmol/g respectively;lipoxygenase increased by 1.04,0.92,0.86 and 0.7 ΔOD234/min-g respectively;polyphenol oxidase increased by 2.67,2.26,1.89 and 1.56 ΔOD420/min-g,respectively;the number of colonies in the blank group > group A > group B > group C.It can be seen that the homemade chlorine dioxide gel retarder has a significant preservation effect on peach and can significantly reduce the decay and deterioration of peach during storage;the larger the release surface area of the gel with the same content,the more beneficial to preservation. |
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