| As aroma compounds influence the tea quality and efficiency, for a long time people pay a lot of attention to the related research. Because of complex research methods and high equipment requirements, results are not perfect. The purpose of this paper is to discuss the effect of different aroma extraction methods, producing places, potassium fertilizer management, and machining processes on tea aroma compounds. Through above work, it will not only improve aroma extraction methods, but also provide guidance for tea garden construction, cultivation and processing technology.1. Using different methods (dry-tea aroma method and brewing-tea aroma method), the type of aroma substances, the content of fragrant material and the proportion is quite different. Dry-tea aroma method is better than brewing-tea aroma method. This study selected the extracted temperature, extracted time, tea content, tea forms to analyze the optimal extraction conditions of SPME method. The results showed that the best extracted conditions are selected as following:10g Tea powder (through28mesh fineness),65μm SPME head (DVB/PDMS) extracted60min at60℃water-bath.2. Comparison tea aroma characteristic of three places showed that the amount of total volatile matter of fragrant tea increased by about21%than the low-flavor tea. Alcohols, alkenes and vinyl which are the main part of volatile composition are very different:Alkenes in the low-flavor tea are up to29.36%, while they are only about14%in fragrant tea. The high-flavor tea contains higher alcohols and vinyl material. Compared with the low-flavor tea, the content of alcohols and vinyl in the high-flavor tea increased by49.11-54.18%,32.08-34.46%respectively. In addition, it is found that the content of linalyl, octanol, geraniol, pinene, farnesene in fragrant tea is much higher than that in low-flavor tea. Compared with the low-flavor tea, the content of linalool, octanol and geraniol in fragrant tea increased by301.84-382.41%,78.05-154.12%and51.67-267.39%respectively. Pentanol, heptanal, leafalcohol in low-flavor tea, is much higher than that in fragrant tea sample. Compared with the low-flavor tea, heptanal of fragrant tea reduced by79.14-80.67%。3. Comparison soil characteristic of three places indicated that although pH value, the total content of carbon and nitrogen is insignificant, there is obvious difference in element content. Potassium, magnesium and phosphorus are lower in low-scent tea producing area than high-scent tea producing places. Compared with the upper soil of the low-flavor tea region, the full amount of potassium, magnesium, phosphorus of high-flavor tea places increased by125.62-168.40%,41.69-163.30%and121.53-298.14%respectively. Compared with the lower soil of the low-flavor tea region, the full amount of potassium, magnesium, phosphorus of high-flavor tea places increased by113.05-157.43%,37.60-67.23%and159.55-366.23%respectively. The effective content of above-mentioned elements showed the same rules as the full amount of elements.4. There are few studies related with the effect of potassium on tea aroma compounds. Results showed that Potassium could coordinate the tea aroma material proportion, and improve the quality of tea aroma. After using potassium fertilizer, ocimene, linalool oxide, linalool, benzyl alcohol, β-phenylethanol and nonanal increased. At the same time, pentanol, heptanal, leafalcohol reduced.5. The influence of different levels of potassium fertilizer on aroma substances of tea picking in April showed that with increasing of the potassium fertilizer level, rate of increase of Linalool in tea reached50.34%(A1),61.72%(A2) and81.03%(A3) respectively, and the differentiation between different treatments reached a significant level (P<0.01). Compared with CK1, in A2and A3, the amount of benzyl alcohol increased by24.61%,48.60%, respectively, and β-phenylethyl alcohol increased by30.67%,43.25%respectively. For fatty acids class, aroma with the smell of grass gas (heptanal) reduced and aroma with the smell of flower (nonanal and octanol) increased. The content of above-mentioned aroma substances of tea picking in May and July showed the same rules as tea picking in April.6. The influence of different kinds of potassium fertilizer on aroma substances of zhenongl17showed that two potash fertilizers can both promote ocimene, linalool. linalool oxide, cubebene, longifolene, terpeneol,(3-phenylethyl alcohol increased and the differentiation between different treatments reached a significant level (P<0.05). Compared with CK.2, in B1and B2, the amount of linalool oxide increased by235.64,67.38% respectively, linalool increased by207.31,41.10%respectively, and terpeneol increased by62.20,58.94%respectively. In addition, it is found that the content of linalool, linalool oxide, in B1is much higher than that in B2sample and the content of benzaldehyde (P0.01) β-phenylethyl alcohol in B2is much higher than that in B1sample(P<0.05). The content of above-mentioned aroma substances of longjing43showed the same rules as zhenong117.7. The effect of spreading time on aroma compounds showed that the best spreading conditions are selected as following: In April, picking a bud and two leaves raw tea material, at temperature25℃, humidity66-85℃, spread8to12hours and water content of tea is70-71%. Because at the-above processing, high scent aroma compounds, for example terpene alcohol (linalool, terpeneol), vinyl (cubebene, caryophylene), ketones, and esters are at a higher level, which benefits aroma transformation from grass gas to the faint scent.8. The effect of fixation temperature on aroma compounds showed that tea aroma quality of processing Ⅱ is better than other processings, because the content of aromatic representative substances, especially linalool, geraniol in processing Ⅱ is highest. Compared with processing Ⅱ, in processing Ⅰ and Ⅲ, the amount of linalool induced by45.24,42.04%respectively, linalool oxide(Ⅰ) induced by45.68,32.67%respectively, linalool oxide(Ⅱ) induced by34.89,39.16%respectively, geraniol induced by53.66,56.95%respectively, and β-phenylethyl alcohol induced by15.18,13.90%respectively. Therefore the best fixation conditions are selected as following:processing Ⅱ, water content of tea is at55-60%. |
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