Study On The Inhibition Of The Growth Of Aspergillus Flavus By New Preservation Technology In Licorice

Chinese herbal medicines(CHMs) can be easily contaminated by fungi resulting in the residues of mycotoxins during the processes of growth, harvest, transportation, processing and storage, which not only leads to bad effects on the quality and safety of CHMs and their processed products, but also poses a great threat to human health. Owing to thier low efficiency, poor controllability and other reasons, the traditional preservation techniques are unable to fully meet the modern requirement of the safe storage of CHMs. Therefore, it is great importance and urgency to search for scientific and effective methods to control fungi infection, further to ensure the quality, safety and effectiveness of CHMs. Now, some chemical synthetic fungicides have been frequently used to control the fungal contamination in the preservation of CHMs. However, the contents and types of chemical fungicides allowed for postharvest application are restricted due to their high residual toxicity, long degradation period and pollution to the environment and so on. Therefore, it plays a particularly important role to search and research the high effective, safe and non-toxic, natural, environment-friendly the new preservation technology to control post-harvest fungi in CHMs in the storage process.In this paper, the “in vitro” antifungal and antiaflatoxigenic properties of Litsea cubeba essential oil(LC-EO) upon Aspergillus flavus and the “in situ” inhibitory effects on AFB1 production were evaluated in licorice by volatile assay. Meanwhile, on the basis of the plant essential oil and traditional method of confrontation with the same storage, a new type of “couplet medicines” preservation method for CHMs preservation was put forward,and explored its practicability.The research results are as following:1. Dried fruits of L. cubeba were subjected to hydrodistillation. 51 chemical compositions, representing 98.73% of the total compounds present, were identified in the essential oil by GC-MS method. The main components of LC-EO included(Z)-Limonene oxide(30.14%),(E)-Limonene oxide(27.92%), and D-Limonene(11.86%), which accounted for 69.92% of the total oil composition.2. The “in vitro” inhibitory activity of LC-EO on A. flavus showed that the headspace volatile assay exhibited more effective inhibition against A. flavus mycelial growththan contact assay, and the minimum inhibitory concentration(MIC) and minimum fungicidal concentration(MFC) of LC-EO were 0.5 and 1.0 μL/m L with fumigation, respectively. The LC-EO exhibited a high toxicity against three toxigenic isolates of A. flavus. The hyphae and conidiophores structures of A. flavus underwent alterations, and the fumigated hyphae grow abnormally, were introcession, enation and wilting of the cell surface, following the treated with LC-EO.3. The “in situ” inhibitory effect of LC-EO on A. flavus exhibited that LC-EO could strongly inhibit the growth of A. flavus and the accumulation of AFB1 in licorice. Thus, LC-EO could potentially be used as an antifungal fumigant to control post-harvest fungi in licorice in the storage process.4. On the basis of the plant essential oil and traditional method of confrontation with the same storage, a new type of “couplet medicines” preservation method for the preservation of CHMs was put forward. The orthogonal design experiment was used to analyze the primary and secondary relationship of factors. The results showed that the obtained sequence was as follow: fumigation counter time > relative humidity > counter medicinal herbs > counter dose. The optimum parameters were listed as fumigation counter time of 10 days, relative humidity of 50%, counter medicinal herbs of cubeb, and counter dose of 30 g.