Characterization of the key aroma compounds in black teas with different aroma types by using gas chromatography electronic nose, gas chromatography-ion mobility spectrometry, and odor activity value analysis

Aroma is one of the key factors in evaluating tea quality. However, the dominant aroma components of black teas with different aroma characteristics are still unknown. In this study, the key aroma compounds in black teas with floral aroma, sweet aroma, and sweet & floral aroma were systematically characterized by the combination of gas chromatography electronic nose (GC-E-Nose), gas chromatography-ion mobility spectrometry (GC-IMS), and odor activity value (OAV) analysis. A satisfactory discrimination was obtained by using partial least squares-discriminant analysis, based on the volatile fingerprints from the GC-E-Nose and GC-IMS, with robustness model parameters (R2Y = 0.981, and Q2 = 0.967) and (R2Y = 0.893, and Q2 = 0.86), respectively. Among the 38 identified aroma compounds, 15 volatiles were simultaneously identified as important odorants with OAVs greater than 1 in three fragrant black teas, namely (E)-2-nonenal, linalool, nonanal, benzene acetaldehyde, octanal, benzaldehyde, oct-1-en-3-ol, heptanal, ethyl 2-methylpentanoate, (E)-2-hexen-1-ol, hexanal, 2-methylbutanal, 3-methylbutanal, (E)-3-penten-2-one, and butanal, with ethyl 2-methylpentanoate (176.44≤OAV≤1453.47), 3-methylbutanal (19.59≤OAV≤76.16), (E)-2-nonenal (37.43≤OAV≤56.46) and linalool (3.29≤OAV≤56.72) being the most notable. The results provide a theoretical support for flavor quality improvement and oriented processing of black tea.