Aroma compositions of large-leaf yellow tea and potential effect of theanine on volatile formation in tea

Large-leaf yellow tea (LYT) imparting unique toasty flavor is a traditional beverage in China. The volatile composition of LYT after full fire processing (FF-YT) was determined by different extraction methods. Steam distillation (SD), solid-phase microextraction (SPME) and headspace (HS) were applied for analysis of tea body notes, tea infusion and dry tea aroma, respectively. A total of 143 volatile compounds was identified by the three methods, of which SD-FF-YT, SPME-FF-YT, and HS-FF-YT extracts contained 100, 72, and 56 volatiles, respectively. Heterocyclics and aromatic compounds were the main volatile composition of LYT and might be contributors to its crispy-rice-like odor. l-Theanine was demonstrated to contribute to the formation of tea volatiles. N-Ethylacetamide, formed in the l-theanine only model thermal reaction, was probably involved in the LYT volatile formation. The current results provide new insight into l-theanine on aroma formation, although the detailed formation mechanism remains largely unknown.