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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.

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 1 318 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’.

The aroma and taste profiles of Qingxiang Tieguanyin tea from different regions were determined through sensory evaluation and quantitative descriptive analysis of sensory attributes. By gas chromatography-mass spectrometry (GC-MS), biochemical composition analysis, ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and metrological statistical analysis, the aroma and taste constituents of the tea were determined. The correlation between aroma and taste components and aroma and taste attributes was explored by correlation analysis and regression analysis, and the correlation between taste components and taste attributes was verified through experiments. The results showed that the sensory quality of Qingxiang Tieguanyin tea had regional characteristics and the aroma composition was dominated by terpenoids, followed by esters. Water content, water extract content, total tea polyphenols content and theaflavins content were the major biochemical factors responsible for the taste quality.

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.

In order to investigate the effect of wrapping-rolling on the quality of Tieguanyin oolong tea, non-volatile and volatile metabolites in rolled tea leaves before and after repeated wrapping-twisting for up to three times were analyzed by widely targeted metabolomics based on headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that a total of 973 non-volatile metabolites belonging to 12 categories were identified, including 468 differential metabolites. The total amount of non-volatile metabolites showed a decreasing trend during the wrapping-twisting process. Particularly, the decrease in the content of differential metabolites such as flavonol glycosides and phenolic acids contributed to the reduction in bitterness and astringency during the wrapping-twisting process. The content of differential lipids increased, which provided favorable conditions for the conversion of volatile fatty acids during the subsequent drying process. A total of 47 volatile components belonging to six categories were identified. During the wrapping-twisting process, the contents of β-red myrcene, heptanal, (E)-2-hexenyl hexanoate and cis-3-hexenyl isobutyrate, responsible for fatty or grassy aroma, decreased, while the contents of methyl jasmonate, benzyl benzoate, geranyl acetone and 3,7-dimethyl-1,5,7-octatrien-3-ol, contributing to floral or fruity aroma, increased. It was noteworthy that the odor activity value (OAV) of the major aroma components in Tieguanyin oolong tea, such as linalool, jasmonolactone, cis-jasmonone, α-farnesene and basilene, were still greater than 1 at the end of the wrapping-twisting process although their contents decreased during this process. It could be seen that the wrapping-twisting process was beneficial to purify the quality of Tieguanyin tea, and provided it with a more mellow taste and more obvious floral and fruit aromas. This study provides new insights into the metabolite changes and the flavor formation of oolong tea during the wrapping-twisting process.

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.

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 fruit aroma 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.

BACKGROUND: Lipids are one of the most important bioactive compounds, affecting the character and quality of tea. However, the contribution of lipids to tea productions is still elusive. Here, we systematically identified the lipid profiles of green, oolong, and black teas in purple‐leaf tea (Jinmingzao, JMZ) and green‐leaf tea (Huangdan, HD), respectively. RESULTS: The lipids analysis showed regular accumulation in tea products with different manufacturing processes, among which the fatty acids, glycerolipids, glycerophospholipids, and sphingolipids contribute to the quality characteristics of tea products, including typical fatty acyl (FA), monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerols (DGDG), and phosphatidylcholine (PC). Compared tea materials with products, levels of fatty acids were up‐regulated, while glycerolipids and glycerophospholipids were down‐regulated in tea products. FA 18:3, FA 16:0, MGDG 36:6, DGDG 36:6, PC 34:3, and PC 36:6 were the negative contributors to green tea flavor formation of purple‐leaf tea. The pathway analysis of significant lipids in materials and products of purple‐leaf tea were enriched linolenic acid metabolism pathway and glycerolipid metabolism. CONCLUSION: This study provides insights into the lipid metabolism profiles of different tea leaf colors, and found that fatty acids are essential precursors of black tea flavor formation. © 2021 Society of Chemical Industry [ABSTRACT FROM AUTHOR]