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.

To investigate the differences in the quality of Huangguanyin oolong tea from different geographical origins, the aroma composition of Huangguanyin oolong tea produced in Yunxiao and Wuyishan was analyzed by using electronic nose and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The electronic nose data showed that orthogonal partial least squares-discriminant analysis (OPLS-DA) could distinguish Huangguanyin oolong tea from different geographical origins. By HS-SPME-GC-MS, a total of 79 aroma components were identified, of which 17 aroma components were found to be significantly different between the two production regions and therefore could be used to distinguish the geographical origin of Huangguanyin oolong tea. According to odor activity values (OAV), methyl jasmonate, indole, jasmonone, E-nerolidol and jasmonolacton contributed greatly to the floral aroma of Yunxiao Huangguanyin tea, while linalool, decanal, laurelene, isovaleraldehyde and hexanal contributed greatly to the floral and fruitaroma of Wuyi Huangguanyin tea. The results of geographical origin authentication showed that the discrimination accuracy of the support vector machine (SVM) model based on the 17 differential aroma compounds was only 83.33%, compared to 100% based on five important aroma components (linalool, E-lactone, jasmonolactone, methyl jasmonate and indole). Our results will provide useful information for elucidating the quality characteristics of Huangguanyin oolong tea from Yunxiao and Wuyishan.

In this study, the metabolites in the flowers and leaves of single- and double-petal jasmine were determined and compared by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) combined with multivariate statistical analysis. The results showed that a total of 935 metabolites were identified from all samples, including amino acids and derivatives, phenolic acids, nucleotides and derivatives, flavonoids, lignans and coumarins, tannins, alkaloids, terpenoids, organic acids, lipids, saccharides and sugar alcohols, vitamins, and other compounds. Totally 348 and 337 significantly changed metabolites (SCMs) from the flowers and leaves were identified between single- and double-petal jasmine, respectively. The major SCMs were phenolic acids, flavonoids, lipids, saccharides and sugar alcohols. The leaves of double-petal jasmine were rich in flavonoids. In addition, the flavone and flavonol biosynthesis pathways were more active, leading to accumulation of more compounds with biological and pharmacological activities such as nicotiflorin, cynaroside, quercetin, quercetin-3-O-glucoside, astragalin, and afzelin. Lipids were the major unique metabolites in the flowers and leaves of single-petal jasmine. The unique metabolites in the flowers and leaves of double-petal jasmine were more diverse and abundant than those in single-petal jasmine. The results of this study are very meaningful for guiding the development of jasmine resources.

The aroma components of white tea from the new tea strain ‘Baiyun 0492’ (also known as Baiyun Tezaocha) and ‘Fuyun 6’ as a control were analyzed and compared by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) in an effort to identify the characteristic aroma components of ‘Baiyun 0492’ white tea. A total of 928 aroma compounds were detected in six white tea samples (of three different grades for each type), and nonyl acetate, contributing to floral and fruity aromas, might be an aroma compound unique to ‘Baiyun 0492’ tea. The results of relative odor activity value (ROAV) analysis showed that β-ionone, linalyl acetate, linalool, (Z)-decan-2-enal, damascenone, neral and citral were the key aroma components in both white teas. Based on orthogonal partial least squares-discriminant analysis (OPLS-DA), the contents of linalool, methyl benzoate, hotrienol, nonyl acetate, 3,7-dimethy-6-actenoic acid and geranyl formate in ‘Baiyun 0492’ tea were significantly higher than those in ‘Fuyun 6’ tea (variable important in the projection (VIP) > 1, P < 0.05). Linalsol and methyl benzoate were important aroma compounds of ‘Baiyun 0492’ white tea, responsible for pekoe-like, fruity and floral aromas. This study is helpful for a comprehensive understanding of the aroma characteristics of ‘Baiyun 0492’ white tea, and provides a scientific basis for the research and development of ‘Baiyun 0492’ white tea products with distinctive personality.

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’.

In order to study dynamic changes and variations in aroma between single- and double- petal jasmine flowers (Jasminum sambac) during the opening process, headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS) was used for qualitative and quantitative analysis of jasmine aroma components at different opening periods. The results showed that phenylacetaldehyde, methyl anthranilate, methyl benzoate, α-farnesene, benzyl acetate were the major aroma components of jasmine flower. The contents of aroma components such as β-ethyl phenylacetate, methyl anthranilate, α-stigmasterol and α-farnesene in single-pedal jasmine flowers initially increased and subsequently decreased during the opening process, and so did the contents of aroma components such as benzyl acetate, cis-3-hexenyl benzoate and benzyl benzoate in double-petal jasmine flowers, being higher at the end than in the beginning of the opening period. In addition, benzaldehyde, phenylacetaldehyde, and β-ethyl phenylacetate were the key substances responsible for the fresh and clean aroma of single-pedal jasmine flowers, while hexyl benzoate, cis-3-hexenyl benzoate, and α-farnesene were the key substances contributing to the strong floral aroma of double-petal jasmine flowers. This study provides a basis for the application of single-pedal jasmine flowers in jasmine tea production.

In this study, the tender shoots of ‘Jinmudan’ tea plants harvested in summer and autumn were processed separately into green tea, yellow tea, white tea, oolong tea and black tea. Headspace-solid phase microextraction (HSSPME) combined with gas chromatography-mass spectrometry (GC-MS) was used to determine and analyze the volatile metabolites in the 10 tea samples. The results showed that 522 volatile metabolites were identified in the summer tea, mainly including terpenes, esters and alcohols, and 502 volatile metabolites in the autumn tea, mainly including terpenes, esters and heterocyclic compounds. The analysis of odor activity value (OAV) showed that β-ionone, α-ionone, decanal, methyl benzoate and geraniol were the key aroma substances of Jinmudan green tea; β-ionone, 2-ethoxy-3-methylpyrazine, decanal, methyl benzoate and geraniol were the key aroma substances of Jinmudan yellow tea; geraniol, phenylacetaldehyde, methyl salicylate (E)-linalool oxide, and 2-ethoxy-3-methylpyrazine were the key aroma substances of Jinmudan white tea; indole, methyl benzoate, phenylacetaldehyde, geraniol, and (E)-linalool oxide were the key aroma substances of Jinmudan oolong tea; geraniol, linalool, phenylacetaldehyde, methyl benzoate, and methyl salicylate were the key aroma substances of Jinmudan black tea. The contribution, type and quantity of aroma substances in the autumn tea were greater than those in the summer tea. The OAV of 42 key aroma substances such as geraniol, methyl salicylate and phenylethanol in the autumn tea samples were higher than those in the summer tea samples. Overall, flowery aroma was the major aroma type of Jinmudan tea, and the aroma quality of the autumn tea was better than that of the summer tea. Totally 14 volatile metabolites such as geraniol, linalool, 2-ethoxy-3-methylpyrazine and methyl benzoate were the key aroma substances of the ‘Jinmudan’ tea variety.

In this study, sensory evaluation, high performance liquid chromatography (HPLC), high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) were employed to analyze the major flavor components of different aroma types of Anxi Huangjingui tea. The results indicated that Anxi Huangjingui tea had an intense aroma as well as a mellow and sweet aftertaste. Each type of Anxi Huangjingui tea had their own unique sensory characteristics. Specifically, the light-aroma type had a long-lasting refreshing fruity aroma and a fresh, mellow, sweet, and brisk aftertaste, whereas the strong-aroma type had a strong sweet aroma and a heavy, mellow, sweet, and brisk aftertaste. A total of 61 differential aroma compounds were identified between the two aroma types. The light-aroma type showed significantly higher aroma character impact (ACI) values for methyl heptenone, methyl salicylate, hexanal, and isoamyl alcohol than did the strong-aroma type. Combining this finding with their odor activity values (OAV), we inferred that the above four compounds were key contributors to fresh, floral, and fruity aromas. Meanwhile, dehydrolinalool, myrtenol, 2,5-dimethyl-3-ethylpyrazine, 2-acetyl-3-methylpyrazine, limonene, and crocinaldehyde exhibited significantly higher ACI values in the strong-aroma type, indicating that these compounds may contribute to baked, floral, and fruity aroma characteristics. This study provides a scientific basis for understanding the flavor characteristics of Anxi Huangjingui tea with different aroma characteristics.