Study On The Optimum Extraction And Activities Of Citrus Essential Oils

Citrus essential oils are important natural spices with abundant resources.They are usually used in food production and processing as aromatic agents.However,the theoretical basis of citrus essential oils as natural preservatives in food preservation is not clear,and there are problems of poor quality and low yield in the actual production of citrus essential oils.In the first part of this study,peel essential oils of Yunnan finger citron,Guangxi finger citron,Jinhua finger citron,Nanfeng mandarin,ponkan,grapefruit,shaddock,Italian bergamot,Taiwan bergamot,orange,lemon and citron were extracted by cold-pressed method.The differences in composition and biological activities of citrus essential oils were analyzed.The results showed that the components of the essential oils were different,but they all showed good biological activities.Secondly,based on response surface methodology(RSM),the extraction process parameters of Nanfeng mandarin peel essential oil by cold-pressed method were optimized: calcium hydroxide was selected as the soaking agent,the ratio of material to liquid was 1:5,the crushing degree of peel was 4cm,calcium hydroxide concentration 2.97 h,soaking time 3.68%,sodium chloride concentration 0.12%.Under the optimized condition,the actual oil yield was 0.689±0.01%.Thirdly,the differences of finger citron peel essential oils obtained by cold-pressed,hydrodistillation and supercritical fluid extraction methods were compared.In total,29,24 and 29 components were identified and quantified of the detected constituents in cold-pressed essential oil(CPO),hydrodistillation essential oil(HDO)and supercritical fluid essential oil(SFEO),respectively.There was no significant difference in antioxidant ability between CPO and SFEO,both of which were stronger than HDO.There was no significant difference in the inhibitory effect of the three essential oils on the tested bacteria.In addition,the aroma of SFEO and CPO are close to nature,indicating that supercritical fluid extraction can replace cold-pressed method to extract finger citron essential oil.Finally,the flower,peel and leaf essential oils of finger citron were applied to preserve steamed bun.The results showed that the antioxidant activity of finger citron leaf essential oil was better than that of peel and flower essential oils.Leaf essential oil had the strongest antifungal activity against the five fungi causing steamed bread mildew,and changed the mycelial structure and extracellular conductivity to the greatest extent than the other two oils.In addition,the accelerated storage test showed that the three essential oils could prolong the shelf life of steamed bun by 4-5 days,3-5 days and 11-13 days,respectively.The results of this subject indicated that citrus essential oils have good biological activities.They can be used as natural preservatives to prevent food spoilage and prolong their storage and shelf life,and provide some theoretical references for further study of other active effects of citrus essential oils.