| Blue mold caused by Penicillium italicum is one of the most important diseases of citrus during storage,and it is easy to spread and will lead to a large number of citrus fruit rot,resulting in huge economic losses.Although traditional chemical fungicides can prevent the occurrence of blue mold in citrus,overuse of such fungicides can easily cause food safety problems.As plant extracts,perillaldehyde and vanillin have been certified as food additives and can be used in food industry,and both of them have certain antibacterial activity.Based on this premise,this study preliminarily discussed the mechanism of perillaldehyde and vanillin inhibiting P.italicum,and in vivo inoculation and storage experiments of citrus fruits were carried out.The main research results are as follows:1.The minimum inhibitory concentration(MIC)and minimum fungicidal concentration(MFC)of perillaldehyde on P.italicum were 0.4μL/m L and 0.5μL/m L,respectively;The minimum inhibitory concentration(MIC)and minimum fungicidal concentration(MFC)of vanillin against P.italicum were 0.8 g/L and 0.9 g/L,respectively.In the spore germination test,perillaldehyde and vanillin could significantly reduce the spore germination rate of P.italicum.By observing the mycelium morphology and cell structure under the electron microscope,it was found that the growth of P.italicum mycelium treated with perillaldehyde and vanillin was inhibited,the cell wall and membrane of mycelium were damaged to varying degrees,organelle were difficult to distinguish,and there were many vacuoles in the cells.Due to changes in the cell membrane of the mycelium,intracellular ions leak out,causing a significant increase in electrical conductivity,accompanied by leakage of nucleic acid and protein,resulting in disorder of the Internal environment of the mycelium,overaccumulation of reactive oxygen species,and thus inducing cell apoptosis.2.In vivo experiments,the lesion diameter of the inoculated fruit on the 6th day was measured and it was found that the diameter of diseased spots in the control group was36.09 mm.The diameters of diseased spots on fruits treated with 20 times the minimum fungicidal concentration(20MFC)and 30 times the minimum fungicidal concentration(30MFC)of perillaldehyde were 31.29 mm and 29.56 mm,respectively.There was no significant difference between the treatment group and the control group,indicating that perillaldehyde cannot significantly reduce the diameter of diseased spots on the surface of fruits.The diameter of the diseased spot of the fruit treated with 20 times of the minimum fungicidal concentration(20MFC)of vanillin was 26.94 mm,which was significantly lower than that of the control group,indicating that high concentration of vanillin could significantly inhibit the growth of the diseased spot on the surface of the fruit.3.After the citrus fruits were soaked in vanillin,the fruit storage quality was measured for 90 days,and the weight loss rate in the vanillin treatment group was slightly higher than that in the water treatment group,but there was no significant difference;The contents of soluble solids(TSS)and titratable acid(TA)in vanillin treatment group were significantly lower than those in other treatment groups,The content of vitamin C(V_C)in the vanillin treatment group was significantly higher than that in the water treatment group.The results showed that vanillin treatment could rapidly reduce the TSS and TA content of fruit,but slow down the decline of V_C content.In summary,perillaldehyde has a significant antibacterial effect in vitro,but its prevention and control effect in vivo is not significant.Vanillin has significant antibacterial effect on P.italicum,and provides a new idea for the control of blue mold in citrus,which is expected to be developed as a new type of green fungicide. |
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