茉莉花茶窨制过程水分变化与香气品质变化的相关性分析

为探明茉莉花茶窨制过程水分迁移与香气组分变化规律，以窨花前、通花前、起花前、烘干后的茶样为材料，运用低场核磁共振技术分析水分分布情况结合顶空固相微萃取-气相色谱-质谱技术分析香气成分的组成和含量。结果表明：茉莉花茶窨制过程各个工序含水率差异极显著，除窨花前茶坯外，其他3 个工序的花茶均出现结合水、弱结合水和自由水3 个水分信号峰；结合水是主要的水分状态，峰面积比例呈先上升后下降趋势，且均高于窨花前；弱结合水峰面积比例呈先下降后上升趋势，均低于窨花前；自由水峰面积比例最低，在窨花前茶坯中未发现，在其他3 个工序呈先下降后上升趋势。茉莉花茶窨制过程中共鉴定出75 种香气成分，包括醇类、酯类、烯烃类、醛类、其他类。茶叶窨制过程吸附了茉莉花释放的香气，因此窨制完成烘干后花茶中各个类别香气成分的含量增加，其中酯类含量最高，达到9.721 μg/g，醇类次之，为3.854 μg/g，再者是烯烃类含量达到3.377 μg/g，且种类最丰富，达到26 种。与JTF（茉莉花茶香气）指数相比，XFJTF（茉莉花茶香气品质评价得分）指数呈“升-降-升”趋势，且其他3 个工序的XFJTF指数值均高于窨花前，更适合评价茉莉花茶香气品质。相关性分析发现：结合水峰面积、弱结合水峰面积与醇类含量均呈正相关，自由水峰面积与酯类含量呈极显著负相关，与烯烃类含量呈极显著正相关。本研究为丰富茶叶吸香机理和调控茉莉花茶生产工艺参数提供一定理论依据。

Correlation Analysis of Moisture Content and Aroma Quality in the Scenting Process of Jasmine Tea

In order to explore the migration of moisture and the variation in aroma components during the scenting of jasmine tea, tea samples before scenting, before heat release, before flower pick-out and after drying were analyzed for water distribution by low-field nuclear magnetic resonance (NMR), and the composition and content of aroma components in these samples were determined by headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). The results showed that the moisture content of jasmine tea was significantly different at different stages of scenting, and all tea samples except tea base before scenting exhibited the signal peaks of bound water, immobilized water and free water. Bound water was the major water state, and the proportion of peak area of bound water tended to increase initially and then decrease, and was higher than that before scenting. The proportion of peak area of immobilized water decreased first and then increased, and was lower than that before scenting. The?proportion of peak area of free water was the lowest and not found before scenting, and presented a trend of first decreasing and then increasing during scenting. A total of 75 aroma components were identified in the jasmine tea scenting process, including alcohols, esters, alkenes and aldehydes. The aroma released from jasmine flowers was adsorbed by tea, so the content of aroma components increased in jasmine tea after drying. Among them, the content of esters was the highest (9.721 μg/g), followed by alcohols (3.854 μg/g), and alkenes (3.377 μg/g), and the number of alkenes was the largest (26). The score for aroma quality of jasmine tea increased, then decreased and increased again during scenting, and was higher than that before scenting, which was more suitable than aroma index for evaluating the aroma quality of jasmine tea. Correlation analysis showed that the peak areas of bound water and immobilized water had a positive correlation with the relati contents of alcohols, and the peak area of free water had a significantly negative correlation with the contents of esters but a significantly positive correlation with the contents of alkenes. The results provide a theoretical basis for enriching the knowledge about the aroma adsorption mechanism of jasmine tea and regulating the processing parameters of jasmine tea.