To investigate the differences in aroma among five high-fragrance black teas (Tieguanyin, Jinguanyin, Jinmudan, Huangdan and Meizhan), an electronic nose, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) and sensory evaluation were used to investigate their key aroma components. The sensory evaluation results showed that all black teas had obvious aroma characteristics. Jinmudan black tea had a prominent fruity and floral aroma with a faint milky note. Jinguanyin black tea had a rich floral aroma with elegant fragrance. Tieguanyin black tea had a tender, sweet and milky aroma. Huangdan black tea had a sweet aroma with floral notes. Meizhan black tea had an obvious fresh and sweet aroma. Orthogonal partial least squares-discriminant analysis (OPLS-DA) performed on the electronic nose data showed a clear separation among different black teas. By HS-SPME-GC-MS, a total of 834 aroma components were identified, and 272 differential aroma compounds were selected using the cutoff of variable importance in projection (VIP) > 1 with a P value < 0.05. According to odor activity value (OAV) and relative odor activity value (ROAV), benzenemethanethiol, 3-mercapto-3-methylbutyl formate, dimethyl trisulfur compounds, 3-octen-2-one, (Z)-6-nonenal and 2-thiophenemethanethiol were identified as key aroma components in the five black teas, which contributed to their clean, sweet, floral and fruity aroma characteristics. Among them, 1-(2-thienyl)-ethanone, 3-octen-2-one and 3-mercapto-3-methylbutyl formate were important volatile substances to discriminate between different black teas. The findings of this study help to elucidate the aroma characteristics of different varieties of black tea and also provide a scientific basis for the research and development of high-fragrance black tea.

This study used widely targeted and targeted metabolomics based on headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) to analyze the non-volatile metabolites, volatile metabolites, and major quality components in congou black teas produced from the high-aroma black tea cultivars‘Jinmudan’ and ‘Jinguanyin’, and it explored the differences in chemical characteristics between the two teas. The results showed that a total of 1318 non-volatile metabolites were identified in the two teas, and the differential metabolites between them were most enriched in flavonoid-related synthesis pathways. Among them, catechins and quercetin-3-O-glucoside were significantly upregulated in ‘Jinmudan’ black tea, while chrysin and apigenin-7-O-neohesperidoside were significantly upregulated in ‘Jinguanyin’ black tea. A total of 759 volatile compounds were identified, among which 12 compounds, including β-ionone, geraniol, decanal and methyl benzoate, were the key aroma components of both teas. The results of relative odor activity value (ROAV) analysis indicated that aroma components such as indole, δ-decanolactone, trans-nerolidol, phenylacetaldehyde and jasmonone responsible for floral, fruity and milky aroma characteristics were more abundant in ‘Jinmudan’ black tea, which may be the key compounds contributing to the floral, fruity and peach-like aromas of ‘Jinmudan’ black tea. Aroma components such as methyl salicylate, (Z)-3-hexenol, and hexanol responsible for fresh and floral aromas were more abundant in ‘Jinguanyin’ black tea, which may be the key compounds contributing to its long-lasting aroma. The results of this study are helpful to elucidate the flavor and quality characteristics of ‘Jinmudan’ and‘Jinguanyin’ black tea, providing a scientific basis for the development of black tea products from the excellent high-aroma tea cultivars ‘Jinmudan’ and ‘Jinguanyin’.