Fujian Shuixian belongs to the semi-tree form of tea plant (Camellia sinensis), which is the main variety for processing Wuyi Rock Tea (WRT). At present, there is a widely phenomenon that Shuixian grows naturally (no-pruning) in the management of tea gardens of Wuyishan, and its quality is obviously different from that of pruned Shuixian. In order to clarify the basis and differences of aroma and flavor substances WRT under natural growth and pruning conditions, this study used gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC) technology, combined with multivariate statistical analysis, to explore the internal relationship among aroma substances, flavor components and quality of WRT before baking (raw tea) and after baking (finished tea) under natural growth and pruning conditions. The results showed that 261 volatile compounds were identified by GC-MS technology. It reveals that there are obvious differences in aroma substances between raw tea and finished tea of the natural growth Shuixian and pruned Shuixian with the help of principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). Compared with the raw tea of pruning Shuixian, the raw tea of natural growth Shuixian showed significant differences in 41 volatile substances (Selection standard: VIP>1, and the FC≥1.5 or the FC≤0.67), in which the relative content of hexyl hexanoate, plant alcohol, isophytol, trans-nerolidol are higher, however, the relative content of β-cedrene, γ-junitene and 2-methoxyfuran are lower. Compared with the finished tea of pruning Shuixian, the finished tea of natural growth Shuixian showed significant differences in 71 volatile substances, such as hexyl hexanoate, methyl caproate, trans-nerolidol, (Z)-β-farnesene, 1-heptanol, 2-heptanone with fruity aroma, and 3-ethyl-1H-pyrrole, 2-formyl-4with baking aroma, whose relative content are higher. There are also great differences in aroma substances between natural growth Shuixian and pruned Shuixian before and after baking, with 91 and 70 different substances respectively. The analysis of aroma activity value (OAV) showed that (E)-3-hexenol, indole, trans-nerolidol, epoxy-β-ionone, (E)-linalool oxide, 2-phenylethanol and methyl salicylate may be important substances for the aroma formation of natural growth Shuixian. Analysis of the main flavor substances showed that there were obvious differences in catechin components and caffeine between natural growth Shuixian and pruned Shuixian. The results of sensory evaluation are consistent with the results of physical and chemical test, showing that natural growth Shuixian with rich fruit fragrance, mellow taste and better quality. This study has a guiding role in scientific management of tea gardens and tea quality control.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |