College of Life Science, Ningde Normal University, Ningde 352000, China.
Key Laboratory of Tea Science in Fujian Province, College of Horticulture, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Molecules. 2022 Jul 4;27(13):4298. doi: 10.3390/molecules27134298.
As important factors to oolong tea quality, the accumulation and dynamic change in aroma substances attracts great attention. The volatile composition of oolong tea is closely related to the precursor contents. Fatty acids (FAs) and their derivatives are basic components of oolong tea fragrance during the postharvest process. However, information about the precursors of FAs during the postharvest process of oolong tea production is rare. To investigate the transformation of fatty acids during the process of oolong tea production, gas chromatograph−flame ionization detection (GC-FID) was conducted to analyze the composition of FAs. The results show that the content of total polyunsaturated FAs initially increased and then decreased. Specifically, the contents of α-linolenic acid, linoleic acid and other representative substances decreased after the turn-over process of oolong tea production. The results of partial least squares discrimination analysis (PLS-DA) showed that five types of FAs were obviously impacted by the processing methods of oolong tea (VIP > 1.0). LOX (Lipoxygenase, EC 1.13.11.12) is considered one of the key rate-limiting enzymes of long-chain unsaturated FAs in the LOX-HPL (hydroperoxide lyase) pathway, and the mechanical wounding occurring during the postharvest process of oolong tea production greatly elevated the activity of LOX.
作为乌龙茶品质的重要因素，香气物质的积累和动态变化引起了极大的关注。乌龙茶的挥发性成分与前体含量密切相关。脂肪酸（FAs）及其衍生物是乌龙茶在采后过程中香气的基本组成部分。然而，关于乌龙茶采后过程中 FAs 前体的信息却很少。为了研究脂肪酸在乌龙茶生产过程中的转化，采用气相色谱-火焰离子化检测（GC-FID）分析 FAs 的组成。结果表明，总多不饱和脂肪酸的含量先增加后减少。具体来说，乌龙茶生产过程中转式后，α-亚麻酸、亚油酸等代表性物质的含量下降。偏最小二乘判别分析（PLS-DA）的结果表明，有 5 种 FAs 明显受到乌龙茶加工方法的影响（VIP>1.0）。LOX（脂氧合酶，EC 1.13.11.12）被认为是 LOX-HPL（过氧化物裂解酶）途径中长链不饱和 FAs 的关键限速酶之一，而乌龙茶采后过程中发生的机械损伤大大提高了 LOX 的活性。
