| Aroma plays an important role on the quality of tea. It consists of many volatile compounds, whose content is little. The interactions of many factors determine the aroma of tea. This study is to measure the volatile compounds of the fresh and dry tea with different varieties and the tea samples of different drying methods and temperature treatments, using headspace solid-phase microextraction and GC-MS. The results showed as follow:1. The content of alkenes and alcohols of dry tea increased significantly, compared with that of fresh tea. Alkenes increased235.63%and124.00%, respectively in Jiukeng and Zhenong113. In addition, terpene alcohols and aldehydes with favorable aroma of the dry tea of Jiukeng and Zhenong113increased significantly, Linalool increased61.03%and119.01%, Nonanal ncreased157.13%and100.54%, respectively. Geraniol and a-farnesene generated in processing technology, whose contents were2.13%and6.08%respectively in dry tea of Jiukeng. Meanwhile, Grass fatty alcohols and aldehydes with low-boiling decreased significantly or were not detected, the content of grass alcohols decreased74.72%and74.25%in the two varieties respectively.2. The content of alkenes and ketones in fresh and dry tea of Jiukeng and Zhenong113had significant difference, as well as that of aldehydes. The content of alkenes in fresh tea of Zhenong113was higher117.90%than that of Jiukeng, as well as the dry tea was higher45.42%. The content of terpene alcohols of the two varieties also showed significantly difference, Linalool in the dry tea of Jiukeng was higher51.62%than that of Zhenong113. In addition, the content of Geraniol and Nerolidol and so on also had significant difference. The content of fatty alcohols and aldehydes also had significant difference, Nonanal in the dry tea of Jiukeng was higher59.96%than that of Zhenong113.(3-farnesene and Benzaldehyde were not detected in the dry tea of Zhenong113. In conclusion, the change of the content and varieties of volatile compounds influenced the aroma difference of different varieties. 3.Effect of drying methods on volatile compounds of tea samples showed that the content of terpene alcohols with favorable aroma of baking-roasting-baking treatment was significantly higher than that of only roasting, roasting-baking-roasting and only baking, Linalool was higher101.47%,78.89%and5.64%.Aromatic alcohols was higher255.63%,66.07%and32.80%. Geraniol was higher169.67%,117.88%and25.40%. The content of favorable alcohols of only baking was only lower than that of baking-roasting-baking and its content of fatty alcohols and aldehydes was the highest. The content of favorable alcohols of roasting-baking-roasting was significantly lower than that of only baking. The content of pyrazines of only roasting samples was11.47%.while other treatments were not detected. Sensory evaluation results of tea samples showed than the aroma of baking-roasting-baking treatment is high and brisk. Therefore, the best drying method is baking-roasting-baking.4. Effect of the initial temperature(70℃,90℃,110℃and130℃)on the volatile compounds of tea samples showed that the content of fatty alcohols and aldehydes with low-boiling in the sample of70℃treatment was the highest, and grass alcohols and aldehydes were not detected in that of130℃treatment, whose nonanal was lower62.46%,62.88%and65.37%than that of70℃and90℃as well as110℃treatment. Pyrazines and pyrroles were only detected in the sample of130℃treatment, and the total content was8.14%.Meanwhile,The content of terpene and aromatic alcohols in the tea of90℃and110℃treatment was very high, Geraniol was higher81.31%and72.72%in the tea of110℃treatment, compared with that of70℃and130℃treatment, while benzyl alcohol was higher49.12%and23.19%, respectively. Sensory evaluation results showed the aroma score of the sample of90℃and110℃treatment was high. therefore, the appropriate initial temperature was between90℃and110℃.5. Effect of the the repeated temperature treatments on volatile compounds of the tea showed that the higher of repeated temperature treatment, the lower of the content of fatty alcohols and aldehydes, the more of the content of pyrazines. When the repeated temperature was110℃, the pyrazines were detected. The content of pyrazines of the samples of70-110℃and110-110℃treatment was2.24%and5.85%respectively. The content of terpene and aromatic alcohols in the tea of110-90℃treatment were the highest. While the content of a-cubebene was higher247.27%,111.44%and1069.39%than that of110-70℃and110-110℃as well as110-130℃treatments, while Geraniol was higher153.37%,182.88%and166.45%. Meanwhile, the content of terpene and aromatic alcohols in the tea of90-90℃treatment was higher than that of90-110℃treatment, a-cubebene and a-farnesene were higher197.55%and130.65%respectively. The content of terpene alcohols of70-110℃treatment was higher than that of70-70℃treatment. Meanwhile, the content of Pyrazines of130-110℃and130-130℃treatment was12.05%and20.53%. Sensory evaluation results showed the aroma score of the sample of90-90℃and110-90℃is higher than that of other treatments. Therefore, to choose90℃as repeated temperature was better. |
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