Study On Extraction Methods Of High Fidelity For Tea Essential Oil And Slow-release Of Aroma

Tea aroma is an important indicator to determine the value of tea, and a key factor in the evaluation of tea quality. Tea essential oil is a mixture of volatile substances in tea extraction by separation and concentration. And it is very volatile, poor stability that result in deterioration of flavor quality during extraction and storage process. Therefore, a reasonable and appropriate method of keeping its original flavor and aroma slow-release is necessary. This paper based on an improved SDE method, used oolong tea Huangjingui as material to optimize the extracting conditions and perfect the tea oil extraction method of high fidelity. Moreover, the effect of fixative (diethyl phthalate, benzyl benzoate and vanillin) in tea essential oil and their role on the performance for aroma slow-release in tea essential oil were studied and detected by GC-MS and olfactory evaluation as well.The results showed that:the optimum condition of SDE improved method to get high fidelity Huangjingui tea essential oil was extraction of 25g tea by continuous 100° C steam in 2 hours. The reason for high fidelity of flavor was that the principle of this extraction method was similar to the national standard method of tea sensory evaluation.The volatilization of aroma components in Huangjingui tea essential oil showed a trend of approximate coordinated evaporation. However, this coordination was broken by adding fixative, and components with different functional groups vaporized at different degrees.The persistence of fragrance was improved by using this 3 kinds of fixatives independently. Among this, tea essential oil with diethyl phthalate showed highest fidelity of original odor type. Vanillin, showed best performance for aroma slow-release but lowest fidelity. Benzyl benzoate had excellent coordinate ability and elegant flavor that made it suitable for blending and enhancing the richness of the aroma.The results of GC-MS analysis of flavor showed that:the proportion of three odor type components (flower, green, sweet) almost unchanged during evaporation and not affected by fixative. The formulation containing 3 fixatives in this proportion got high score of fidelity, insistence, richness, persistence and preference for Huangjingui tea essential oil. The efficiency of 3 fixatives mixture in appropriate proportions was better than single fixative of equal concentration.The practicability of the application of this method for green tea (Longjing, Tangji) and black tea (Keemun, Dianhong) essential oil aroma slow-release was studied as well. Olfaction evaluation results showed that:diethyl phthalate was suitable for this 4 kinds of tea essential oil and can maintain the original flavor. Benzyl benzoate can be used to delay the release of aroma of Dianhong tea essential oil and coordinate to the flavor of tea. Vanillin may reduce the richness of flavor that not be a good choice.