Effect of High-temperature and Long-time Final Roasting on Aroma of Roasted Green Tea

To investigate the effect of high-temperature and long-time final roasting on the aroma quality of roasted green tea, tea samples processed with different final roasting temperatures and durations were evaluated by sensory evaluation and characterized by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry for their sensory aroma and volatile organic compounds (VOCs). The result of sensory evaluation showed that the eight tea samples were classified into four categories according to their characteristic odors, which suggests that final roasting temperature and duration influenced the aroma of roasted green tea. Totally 58 VOCs were identified among all samples, 45 of which were aroma components shared by these samples. The sample distribution patterns generated by unsupervised clustering analysis on the basis of the 58 VOCs were consistent with those based on sensory evaluation. In addition, 32 VOCs were selected as the key contributors to the aroma differences among samples by one-way analysis of variance (ANOVA) and partial least squares-discriminant analysis (PLS-DA). Two-way ANOVA was further applied to investigate the effect of roasting temperature and duration on the contents of the 32 key VOCs. It was found that the contents of 17 key aroma compounds were significantly affected by roasting temperature, duration and the interaction between them (P < 0.05). The contents of 12 key compounds were significantly affected by roasting temperature and duration (P < 0.05). The contents of α-cubebeneand δ-cadinene were significantly affected by the interaction between roasting duration and temperature (P < 0.05), while the content of α-calacorene was significantly affected only by roasting temperature (P < 0.05).