Inhibitory Effects Of Litsea Cubeba Essential Oil And Its Hydroxypropyl-β-cyclodextrin Inclusion Complex On Penicillium Italicum In Citrus

Citrus is sweet and nutritious,which is deeply loved by consumers.However,it is easy to be infected by pathogens after harvest,resulting in fruit decay and economic losses.Penicilliosis is a serious disease of citrus during storage.At present,chemical fungicide is the best method to control this disease.However,chemical fungicides are easy to remain and will produce drug resistance when used in large quantities.Therefore,it is necessary to develop efficient,safe and cheap natural preservatives.Litsea cubeba essential oil（LCEO）is a kind of natural plant essential oil with citral as the main component.It has the advantages of no chemical residue and broad-spectrum bacteriostasis.In this paper,the antibacterial effect of LCEO on Penicillium italiana and its mechanism were studied,and the inclusion complex was prepared by inclusion of LCEO with hydroxypropyl-β-cyclodextrin（HP-β-CD）,and the preservation of Shatang mandarin after harvest was also studied.The main results are as follows:（1）LCEO had significant inhibitory effect on Penicillium italiana,with MIC value of 1.17 mg/mL.LCEO treatment significantly inhibited mycelial growth and spore germination of Penicillium italicum.In addition,the in vivo experiment results showed that LCEO treatment could significantly reduce the incidence of citrus and the diameter of disease spots,and had certain control effect on the occurrence of penicilliosis on citrus fruits.（2）The antibacterial mechanism of LCEO against Penicillium italicum was preliminarily explored.The results showed that the OD₂₆₀value,extracellular conductivity and p H value of Penicillium italiana were significantly increased after LCEO treatment,indicating that the permeability of cell membrane was increased after LCEO treatment,and nucleic acid and other intracellular substances were leaked out.The morphology of mycelium observed by SEM showed that the mycelium lost linearly after LCEO treatment,and irreversible morphological changes such as distortion and shrinkage appeared on the mycelium surface.PI staining results showed that some spores of Penicillium italiana with visible red fluorescence could be observed after LCEO treatment,indicating that LCEO treatment could destroy the integrity of cell membrane.（3）LCEO/HP-β-CD inclusion complex was prepared by saturated aqueous solution method,and the physical and chemical properties of the inclusion complex were characterized by FT-IR,XRD,SEM,particle size determination and TG-DSC.The formation of LCEO/HP-β-CD inclusion complex was confirmed,and the thermal stability of LCEO was significantly improved after inclusion.The antifungal activities of LCEO/HP-β-CD inclusion complex and LCEO/HP-β-CD inclusion complex preliminarily compared.The results showed that LCEO/HP-β-CD inclusion complex could effectively inhibit fungal growth.In addition,the effects of LCEO inclusion complex as preservative on postharvest quality of Shatang mandarin were also studied.The results showed that LCEO inclusion complex could maintain postharvest quality of Shatang mandarin fruits better,but compared with LCEO/HP-β-CD inclusion complex,LCEO/HP-β-CD inclusion complex could maintain postharvest quality of Shatang mandarin fruits more effectively.