State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 130 Changjiang Ave W., Hefei, Anhui 230036, People's Republic of China; International Joint Laboratory on Tea Chemistry and Health Effects, Anhui Agricultural University, 130 Changjiang Ave W., Hefei, Anhui 230036, People's Republic of China.
State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 130 Changjiang Ave W., Hefei, Anhui 230036, People's Republic of China; International Joint Laboratory on Tea Chemistry and Health Effects, Anhui Agricultural University, 130 Changjiang Ave W., Hefei, Anhui 230036, People's Republic of China.
Food Chem. 2018 Oct 15;263:18-28. doi: 10.1016/j.foodchem.2018.04.117. Epub 2018 Apr 27.
l-Theanine, the most abundant amino acid in tea, is widely believed to be associated with the tea taste, however, its contribution to the formation of tea aroma is still unknown. Volatiles were determined and nitrogen-containing compounds formed during manufacturing processes were quantified. Lower levels of total sugar and l-theanine were detected in the Oolong tea product undergoing full fire processing (FFOT) suggesting that l-theanine probably involved in the volatile formation during manufacturing processes. Methylpyrazine and 2,5-dimethylpyrazine, two newly formed compounds in FFOT, together with other volatiles were successfully detected in a model thermal reaction of d-glucose and l-theanine (GT-MTR) but not detectable in thermal reactions with single d-glucose (G-MTR) or l-theanine (T-MTR). The concentration of 2,5-dimethylpyrazine increased significantly by adding additional l-theanine to 2nd roasted tea. Our study demonstrated that l-theanine, at least partly, contributed to the formation of 2,5-dimethylpyrazine, a key roasted peanutty flavor in Oolong tea.
茶氨酸是茶叶中含量最丰富的氨基酸，被广泛认为与茶叶的味道有关，但它对茶叶香气形成的贡献尚不清楚。本研究测定了挥发性成分，并定量了加工过程中形成的含氮化合物。在全火加工（FFOT）的乌龙茶产品中，总糖和茶氨酸的含量较低，这表明茶氨酸可能参与了加工过程中的挥发性物质形成。在 d-葡萄糖和茶氨酸（GT-MTR）的模型热反应中成功检测到了 FFOT 中两种新形成的化合物——甲基吡嗪和 2,5-二甲基吡嗪，以及其他挥发性物质，但在 d-葡萄糖（G-MTR）或茶氨酸（T-MTR）的单独热反应中则无法检测到。向第二次烘焙茶中添加额外的茶氨酸可显著增加 2,5-二甲基吡嗪的浓度。本研究表明，茶氨酸至少部分参与了 2,5-二甲基吡嗪的形成，2,5-二甲基吡嗪是乌龙茶中关键的烤花生风味物质。
