| Citrus is an important economic crop with many varieties,including mandarin,lemon,orange,pomelo and kumquat,etc.Citrus essential oil has not only complex components,but also a wide range of biological characteristics and medicinal values,such as antioxidant,antibacterial,anticancer,analgesia,lowering blood lipid,insecticidal and repellent insects.Therefore,it can be used in food processing,plant pest control and the treatment of a variety of human health diseases.In this paper,the volatile components and activities of citrus leaf,peel and fruit essential oils were studied.Specifically,four kinds of citrus essential oils were extracted by hydrodistillation and simultaneous extraction distillation,and their components were analyzed by GC-MS.The volatile components of four citrus young leaves were detected and analyzed by headspace gas chromatography-ion mobility spectrometry(HS-GC-IMS).The antibacterial and antioxidant activities of citrus essential oil extracted by hydrodistillation were studied.In addition,the antibacterial activity of citrus essential oil microcapsule has also been preliminary studied.The main results of this paper are as follows:1.28,33,28 and 37 components were identified in the essential oil extracted from Nanfeng mandarin,Yangshuo kumquat,Xunwu mandarin and Newhall navel orange physiological fruit drop by hydrodistillation,respectively,while 30,41,32 and 42 components were done by simultaneous distillation extraction,and a total of 60 compounds were identified.Limonene(39.99～91.54%)accounted for the largest proportion in each essential oil.The composition and content of different citrus essential oils are quite different,and the component of citrus essential oil obtained by the two methods was mostly similar in type and content,but there were some differences.Essential oils obtained by simultaneous distillation extraction have more components,and some components such as linalool and α-terpinene showed big differences in content.2.Using healthy and Huanglongbing(HLB)infected young leaves of Newhall navel orange and Shatian pomelo as experimental materials,the analysis of their volatile compounds was carried out by HS-GC-IMS technology.A total of 36 volatile organic compounds were identified in orange leaves and 10 in pomelo leaves.From the GC-IMS spectra,it can be seen that the volatile compounds in HLB infected young citrus leaves are more diverse,and most of them are higher in content.Through the comparison of peak signal intensity,significant differences were found in the content of volatile organic compounds in the two orange leaves,including ethyl 2-methylbutyrate,limonene,ethyl acetate,etc.;while limonene polymer and 3-pentanone and its dimmers displayed obvious difference in two types of pomelo leaves.3.In conclusion,the four citrus essential oils showed different antibacterial and antioxidant activities.The antibacterial activity of four citrus essential oils against four common pathogenic bacteria was tested.The results showed that,except for Pseudomonas aeruginosa,Yangshuo kumquat essential oil has strong antibacterial activity against other three bacterias.The diameter of the maximum inhibition zone reached up to 25.39 mm,and the minimum inhibitory concentration was low(1.56～12.5 μL/m L).Compared with other citrus essential oils,Yangshuo kumquat essential oil had the best antibacterial effect;however,Xunwu mandarin had the weakest activity.DPPH and ABTS methods were used to evaluate the antioxidant activity of citrus essential oils.The results showed that the essential oils of Nanfeng mandarin and Xunwu mandarin had better antioxidant activities than others.4.Using Yangshuo kumquat essential oil as the core material,chitosan and sodium alginate as the wall material,the microcapsules were prepared by complex coagulation method to obtain microcapsule products with better embedding rate.The antibacterial activity of the microcapsule was evaluated by agar diffusion method.The results showed that the microcapsule had good antibacterial effect against Staphylococcus aureus and E.coli,and the diameters of antibacterial zone were 16.51 mm and 21.39 mm,respectively.In summary,the study on the composition,biological activity and microencapsulation of citrus essential oils can lay a theoretical foundation for the subsequent research on the value of citrus essential oil components and activity.It also provides reference for the application of citrus essential oil in food preservation,drug development,plant disease and insect control,etc.In addition,our study may contribute to the enhancement of local citrus economy and the development of regional citrus industry. |
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