| Green tea produced in Summer and Autumn is of low quality in taste and aroma.In this work,the additional treatment was employed during tea processing and dynamic changes of aroma was investigated by HS-SPME/GC-MS in order to improve the quality of green tea produced in summer and autumn.For Bud tea,fresh leaves were spreading in air-conditioned and humidity-controlled room;For One bud with two or three leaves and Single leaf or banjhi shoots(low-grade tea), Shaking was introduced into the spreading procedure.(1)Bud tea(high-grade tea):The aroma quality of bud tea increased during the spreading time.After spreading for 5.0h,the change of aroma became stable.The bud tea made from fresh leaves spreading for 12.5h had aroma of flowers.The treatment group was better than control.GC/MS analysis indicated that,alcohols content decreased from 34.68%to 23.25%during the first 2.5h,and reached 14.93%at 5.0h. At spreading time of 10.0h,the alcohols content increased to 22.99%;Esters content increased during all the spreading procedure,from 11.69%to 42.71%for the first 5.0h,and reached the higher content of 49.95%at 7.5h;Aldehydes and ketones content changed little. (2) One bud with two or three leaves(middle-grade tea):The changes of aroma of treatment group were great than the control group,especially during the first 5.0h.The flower scent became obvious at 10.0h,and it became much more stronger at 15.0h.The aroma of fruit appeared after long time treatment.The aroma quality decreased after treatment for more than 20.0h.Analysis indicated that,the content of esters,olefins and indoles in treatment group increased and the content of alkanes decreased.The content of indoles in treatment group was 15.13%,but not detected in the control group.(3)Single leaf and banjhi shoots(low-grade tea): The grassy aroma decreased and the scent of flower appeared.And the light shaking was in favor of the production of flower scent.Single leaf and banjhi shoots had better quality when shook 90,120 and 90 times and spread for 20.0 hours in the air-conditioned room(T:about 20℃;RH:about 70%).Analysis indicated that the content of esters,indoles and nerolidol was higher for the treatment group.The baking experiment showed:after baking,the aroma quality improved and the flower scent became stronger.The aroma quality increased first and then decreased with the extending of baking time.The toast taste appeared after long time baking,especially under high temperature,such as 140℃.Sensory evaluation showed that the tea had better quality when baked 2.0-3.0h at 100℃and baked 1.0-1.5h at 120℃.Analysis indicated that: Baking under 100℃,the content of alcohols and ketones increased during the treatment. Ehydrolinalool increased during the treatment while the content of linalool,farnesene and nerolidol decreased when baked for long time.Baking under 120℃,the content of alcohols reached highest content at 1.5h and then decreased.The content of ketones and aldehydes increased while the content of olefins and alkanes decreased.Ehydrolinalool increased during the treatment while the content of linalool,farnesene and nerolidol decreased when baked for long time,and the compounds with toast taste such as 3-ethylpyrrole and phyllopyrrole gradually formed.The above results indicated that the aroma quality of green tea produced in Summer and Autumn could be improved by modification of processing technique.
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