| Aspergillus Niger is the dominant mold in the storage of paddy.It produces heat and acid in paddy respiration metabolism.When mildew becomes serious,it even produces toxin,which is harmful to human health.As a new type of botanical antimildew,natural plant essential oils have a good application prospect in inhibiting the growth of fungi and the formation of mycotoxins.In this study,Aspergillus Niger HY2,which has strong mildew causing ability,was used as the research object,aiming to screen out strong plant essential oil with strong bacteriostasis in the vapour phase,study the antibacterial mechanism of its main components and the mildew proof effect on paddy,then to provide theoretical reference for the safe storage of paddy.Through the determination of the minimum inhibitory concentration of six plant essential oils,the best antibacterial effect of plant essential oils was screened out.The results showed that the cinnamon essential oil in the vapour phase had the best inhibitory effect on Aspergillus Niger HY2,with the minimum inhibitory concentration as low as 0.00625 ?L/m L.The sweet orange essential oil in the vapour phase was the weakest with the minimum inhibitory concentration as high as 32 ?L/m L.The other four essential oils in the vapour phase had the minimum inhibitory concentration less than 1.2 ?L/m L.Among the six plant essential oils,except fennel essential oil,the antibacterial effect of essential oil in the vapour phase was obviously stronger than that of essential oil in the liquid phase.There was a dose-dependent relationship between the bacteriostatic rate and the concentration of essential oil,and the bacteriostatic rate gradually decreased with the prolongation of time.After treated with cinnamon essential oil in the vapour phase,the metabolic activity and carbon source utilization capacity of Aspergillus Niger HY2 were lower than those of blank group,and the treatment time was more than 2 days,which resulted in irreversible damage to the metabolic function of Aspergillus Niger HY2.The main components in cinnamon essential oil were analyzed by GC-MS,and the antibacterial mechanism of the main components was studied.The results showed that cinnamaldehyde was the main component of cinnamon essential oil,and the relative content was as high as 88.86%.After treated with cinnamaldehyde in the vapour phase for 2 days,the extracellular conductivity of Aspergillus Niger HY2 increased,The leakage of nucleic acid material increased significantly,and the hyphae emitted red fluorescence after PI staining.The results showed that the integrity of the cell membrane of Aspergillus Niger HY2 was damaged.The results of fourier transform infrared spectroscopy scanning indicated that the contents or structure of lipids,proteins and carbohydrates in the hyphae of Aspergillus Niger HY2 were changed.When the concentration of cinnamaldehyde in the vapour phase was higher than 0.1 ?L/m L,the content of malondialdehyde was significantly increased,which caused the damage of membrane lipid peroxidation mediated and then affected the integrity of cell membrane.The decrease of ergosterol content indicates that cinnamaldehyde in the vapour phase inhibits the synthesis of ergosterol in the cell plasma membrane.In addition,the cell wall was damaged,and the activity of extracellular AKP enzyme was significantly increased.The mitochondrial membrane potential,the activities of ATPase and SDH of Aspergillus nuger HY2 were decreased after treated with cinnamaldehyde in the vapour phase for 2 days.The inhibitory rate of 0.00625 ?L/m L cinnamaldehyde in the vapour phase on mitochondrial ATPase activity was 40.94%,and the inhibitory rate on mitochondrial SDH activity was 10.19%Cinnamaldehyde in the vapour phase of different concentrations was used in simulated storage of paddy to study the effect of mildew prevention on paddy.The results showed that cinnamaldehyde in the vapour phase inhibited the growth of Aspergillus Niger HY2 and reduced the number of mildew in paddy under the conditions of temperature 30 ? and relative humidity 85%,and had certain prevention and control effect on mildew during paddy storage.At the same time,the brightness of paddy increased,the fatty acid value decreased,the fat decomposition slowed down,and the amylase activity was significantly increased at 4 and 6 d storage,and the quality of paddy was significantly improved.Cinnamaldehyde in the vapour phase induced the increase of catalase activity and polyphenol oxidase activity,which promoted the improvement of mildew resistance of paddy. |
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