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Black tea is known to contain condensed tannins including catechin (C), epicatechin (EC), and epigallocatechin gallate (EGCG), as well as caffeine (CAF). Some consumers of specific diets avoid consuming tannins or CAF. Therefore, this study aimed to explore the fast and simple development of a method for separating and quantifying tannins and CAF in black tea using microwave-assisted extraction (MAE) followed by high-performance liquid chromatography (HPLC) analysis. MAE, a type of solid-phase extraction recently developed, was used with a modified microwave that simultaneously accommodates up to 24 samples. The effects of various MAE parameters, including microwave irradiation power, temperature, and solvent, were studied, with concentrations measured in mg/kg. The results showed that optimal extraction conditions were achieved at a microwave irradiation power of 1500 W, a temperature of 80°C, and methanol as the extraction solvent. The extracted samples were analyzed using a C18-M-SE reverse phase column (150 × 4.6 mm) with a mobile phase consisting of acetonitrile, methanol, and H3PO4 (1:49:50), and NaH2PO4 (20 mM) at pH 2.5. The three tannin compounds and CAF were separated in less than 10 min. The method demonstrated excellent repeatability (RSD ? 2%, n = 3), accuracy (96.7-102.5%), and was successfully applied to determine tannin content in commercial black tea samples.

Background and Aims: Anxiety is a natural reaction that affects both the mind and body, often accompanied by symptoms, such as sweating, palpitations, and headaches. The present study aimed to compare the anxiolytic effects of herbal teas made from lavender and black tea. Materials and Methods: In this experimental study, 21 male rats weighing 200-250 grams were used. The rats were assigned to three groups (n=7): the control group received plain drinking water, the Camellia sinensis (CS) group received Camellia sinensis (black tea) herbal tea, and the Lavandula angustifolia (LA) group received Lavandula angustifolia (lavender) herbal tea. During the 24 hours before the experiment, the rats in the treatment groups were given herbal teas made from black tea at a concentration of 0.3% (3 grams of leaves in 1 liter of water) and lavender flowers at the same concentration instead of drinking water. Following that, the behavior of rats was assessed for sedative and anxiolytic activities in the Elevated plus maze (EPM). Data were presented as mean±standard error (mean± S.E.M). Data were analyzed in Graph Pad Prism software (version 8) using one-way ANOVA followed by the Tukey test. A p-value of less than 0.05 was considered statistically significant. Results: The time spent in the open arms of the EPM in the LA group significantly increased compared to the control (P

To reveal the chemical composition profile of Camellia ptilophylla, a rare natural low-caffeine tea variety, non-targeted metabolomics based on high-resolution mass spectrometry (HR-MS) was employed to identify the metabolite composition of green tea and black tea from C. ptilophylla and C. sinensis var. assamica. Additionally, the metabolomic differences between the two types of tea and between the two tea varieties were analyzed using principal component analysis (PCA), cluster analysis (CA), and orthogonal partial least squares-discriminant analysis (OPLS-DA). Differential metabolites were identified using standards and database. A total of 152 metabolites were identified in the four tea samples, the major ones being flavonoids (42%). These metabolites were categorized into four clusters. The metabolomic difference between C. ptilophylla and C. sinensis var. assamica was more pronounced than that between green and black teas. Notably, 24 metabolites including theasinensin B isomers, theobromine and 14 flavonoids such as tetrahydroxyxanthone and epitheaflagallin 3-O-gallate, which were more abundant in C. ptilophylla green tea than in C. sinensis green tea, were considered as the characteristic metabolites of C. ptilophylla green tea. In black tea from C. ptilophylla, 40 characteristic metabolites were identified including 25 flavonoids such as gallocatechin-3,5-digallate, tetrahydroxyxanthone and dihydromyricetin; 4 tannins such as theaflavin 3-gallate, theasinensin A isomers and theaflavin 3,3’-digallate; and theobromine. This study provides a reference for further exploration of bioactive compounds in C. ptilophylla.

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’.

Obesity is a metabolic disorder due to over-accumulation of adipose tissue and ultimately becomes a “disease”. Brown adipose tissue (BAT) thermogenesis and white adipose tissue (WAT) browning emerge as a potential strategy of anti-obesity by dissipating energy as heat. However, drugs based on adipose tissue thermogenesis have not been successfully approved yet. In current study, we found that black tea extract (BTE) obtained by patent-authorized manufacturing process prevented body weight gain as novel thermogenic activator with reduction of adiposity, improvement of adipose distribution, and glucose metabolism improvement in diet-induced obesity mice. Mechanismly, anti-obesity effect of BTE depends on promoting BAT thermogenesis and WAT browning with upregulation of uncoupling protein 1 (UCP1), especially visceral adipose tissue (VAT) with browning resistance. Specifically, utilizing in silico approach of network pharmacology and molecular docking, we identified carbonic anhydrase 2 (CA2) in nitrogen metabolism as anti-obesity target of BTE and further elucidated that protein kinase B (AKT) signaling pathway linked CA2 and UCP1. Meanwhile gut microbiota regulation may prompt the CA2-dependent thermogenesis activation. Our findings demonstrated anti-obesity effect of BTE as thermogenic activator through CA2-mediated BAT thermogenesis and WAT browning via CA2-AKT-UCP1 signaling pathway, which could be developed as promising anti-obesity agent with good safety and efficacy.

Abstract An innovative Chardonnay wine flavored with black tea was prepared under optimal ultrasound conditions at 450.0 W for 22.6 min, and its physicochemical features, antioxidant power, total phenolic content, and volatile composition were systematically examined. A total of 165 phenolic and non-phenolic substances were characterized, including 27 newly formed phenolic substances and 10 non-phenolic substances that were not found in both black tea and Chardonnay wine. Catechin was found to be the phenolic compound with the largest amount detected, which was responsible for the potentiated antioxidant activities. The wine exhibited a profile of 44 volatile compounds, with 13 volatiles as odor-active compounds. Black tea infusion resulted in a decline in fruity, fermented and spicy aromas, but an increase in green and citrus odors, while ultrasound processing further intensified these odors. This study anticipated that ultrasound technology could hold promise for crafting flavored wines with heightened functionalities and appealing flavor profiles. Graphical Abstract Ultrasound-assisted infusion of black tea potentiated the antioxidant activity and enriched the volatile and phenolic profiles of Chardonnay wine.

The use of alternative ingredients as supplements to or blends with kombucha tea to improve organoleptic properties and health effects has recently increased. Indian gooseberry fruit is among the most promising alternative raw materials for producing functional kombucha since the berries contain several beneficial substances. In this study, the production of functional kombucha beverages from fusions of black tea and Indian gooseberry fruit homogenate (IGH) was investigated, and the chemical and biological properties of kombucha products were evaluated and compared with those of traditional black tea kombucha products. Chemical composition analysis revealed that IGH contains high amounts of polyphenols (627.4 mg GAE/L or 129.51 mg GAE/g dry weight), flavonoids (98.0 mg QE/L or 9.11 mg QE/g dry weight), and vitamins, specifically ascorbic acid (465.72 mg/100 g fresh weight). It also contains several amino acids, fatty acids, and trace elements. Supplementing or blending black tea kombucha with IGH in the range of 10 %–50 % (v/v) increased the total phenolic content (TPC), total flavonoid content (TFC), and total acidity of the fermented beverages. Several volatile organic compounds associated with the flavor, aroma, and health benefits of kombucha were also detected in black tea and IGH fusion kombucha products. Moreover, the black tea and IGH fusion kombucha products also displayed greater antioxidant and antimicrobial activities than the traditional black tea kombucha. Among the different combinations of black tea and IGH, supplementing black tea kombucha with 20 % IGH was the best combination for producing alternative and unique functional kombucha products with notable nutritional and health benefits.

Fermentation significantly influences the chemical composition of black tea, yet the effects of different fermentation temperatures on non-volatile components and their in vitro hypoglycemic activity are insufficiently studied. This research investigates how varying temperatures (20, 25, and 30°C) affect the bioactive profile and the inhibitory activity of Jinxuan black tea against α-glucosidase and α-amylase. Our results show that lower fermentation temperatures (20°C) lead to elevated levels of key bioactive compounds, including tea polyphenols (9.24%), soluble sugars (8.24%), thearubigins (7.17%), and theasinesin A (0.15%). These compounds correlate strongly with enhanced α-glucosidase inhibition (R = 0.76–0.97). Non-targeted metabolomic analysis revealed that 36 differential metabolites, including catechins, exhibited altered levels with increasing fermentation temperature. Notably, tea fermented at 20°C exhibited superior hypoglycemic activity, with α-glucosidase inhibition (IC50 = 14.00 ± 1.00 μg/ml) significantly outperforming α-amylase inhibition (IC50 = 2.48 ± 0.28 mg/ml). The findings of this research underscore the importance of fermentation temperature in optimizing the bioactive profile of black tea. It is proposed that recommendations for future processing or formulation should emphasize the use of lower fermentation temperatures, aimed at augmenting the health benefits linked to higher polyphenol content and stronger hypoglycemic activity.

Black tea is highly favored by consumers worldwide, with enzymatic reactions being recognized as a pivotal factor influencing tea quality. The role of microorganisms in shaping the composition of black tea has emerged as a focus of research due to their involvement in enzyme catalysis and metabolic processes. In this study, full-length amplicon sequencing combined with qPCR more accurately reflected microbial profile, and Pantoea, Pseudomonas, Paucibacter, and Cladosporium were identified as the main microbial genera. Moreover, by comprehensively analyzing color, aroma, and taste components over time in black tea samples, correlations were established between the dominant genus and various quality factors. Notably, peroxidase activity levels, total soluble sugar content, and tea pigments concentration exhibited significant associations with the dominant genus. Consequently, this microbiological perspective facilitated the exploration of driving factors for improving black tea quality while establishing a theoretical foundation for quality control in industrial production.

Rolling plays an important role in shaping the characteristic quality of black tea. However, the dynamic alterations in volatile compounds during the rolling process remain unclear, which hampers the quality control of black tea. In this study, the dynamic changes of volatile compounds in Congou black tea throughout the rolling process were explored by a combination of GC-E-Nose and GC–MS analysis. The results of PCA and PLS-DA by GC-E-Nose revealed significant alterations in the volatile profiles, particularly at the 15-min rolling stage. A total of 82 volatile compounds including eight categories were identified in Congou black tea during the rolling process. The most abundant volatiles were aldehydes, alcohols, and esters. Through the integration of variable importance in the projection >1 and p

Hypertension is a serious condition that affects both industrialized and developing nations’ public health. It is an important medical condition that can raise the chance of developing heart, brain, kidney, and other problems. Objective: • To evaluate the effect of green tea and black tea on blood pressure (BP). • To compare the levels of BP among black tea- and green tea-consuming hypertensive patients. • To find out the association between effects of green tea- and black tea-consuming hypertensive patients with selected demographic variables. Methodology: A quasiexperimental research design with the purposive sampling technique was adopted to conduct a study among 60 hypertensive patients. Thirty patients consume black tea, and 30 consume green tea. Data were gathered by structured questionnaires using demographic variables and biological parameters. Result: The calculated Student independent ‘t’ test value of t = 3.216 in the post-test shows that there was a statistically significant difference between the post-test levels of systolic BP between the two groups, which was statistically significant at P < 0.01 level. The calculated student independent‘t’ test value of t = 2.986 in the post-test shows that there was a statistically significant difference between the post-test levels of diastolic BP between the two groups, which was statistically significant at P < 0.01 level. Conclusion: Green tea was found to be more effective than black tea in reducing the level of hypertension among the hypertensive clients.

Black tea is the most important in the world tea production, and is very popular in the world tea market. China has abundant tea resources, especially unused tea leaves in summer and autumn, and there are a few new ways to develop them, such as processing black tea or deep processed products. Application of exogenous enzymes with good functional characteristics, can improve the quality of summer and autumn black teas, and their deep processed products. This article reviews that, the current status and existing problems of exogenous enzymes application in black tea processing in recent years, as well as the types and acting mechanisms of frequently-used exogenous enzymes, transformation of tea components catalyzed by exogenous enzymes during withering, rolling, and fermentation in black tea processing. Utilizing exogenous enzymes to promote the synthesis of theaflavins, a unique component of black tea, and the quality changes in deep-processing of black tea, are also summarized. Exploring the enzymatic processing methods, could promote the efficient utilization of tea resources, and regulate quality of summer and autumn black tea, as well as their deep-processed products, in the future.

The aim of the study was to assess the effect of fruit additives on the health-promoting properties of tea infusions. Black and white tea infusions enriched with fruit additives (lemon, quince, strawberry, and sweet pepper) were investigated. To assess the effect of the additives on the properties of the infusions, the content of phenols, antiradical activity, and reducing properties were analysed. The LC-QTOF-MS method facilitated the identification of catechins and the determination of their content. The principal component analysis was used to define the relationship between catechins and the health-promoting properties of the beverages. The research proved that the strawberry and sweet pepper additives improved the quality of the black tea, where the highest antiradical and antioxidant activity was noted. In turn, the additives used for the enrichment of the white tea had a negative effect on its health-promoting properties. The statistical analyses revealed that epicatechin gallate and epicatechin had the greatest impact on the antioxidant properties of the black tea and the white tea, respectively.

In this study, the taste quality difference between high (Ninghong-Jinhao tea, JH, unfolded fresh leaves) and low (Ninghong-Congou tea, CG, unfurled fresh leaves) grades of Ninghong tea (unique black tea) was analyzed from the perspective of sensory omics, non-targeted metabolomics, and chemical dose. JH was characterized by sweetness and mellowness with umami, while CG was characterized by sweetness and thickness. A total of 94 differential metabolites contribute to the quality difference between two grades. Further quantitative analysis revealed that JH exhibited a high accumulation of amino acids, catechins, and theaflavins, while CG demonstrated a high accumulation of water extract, tea polyphenols, flavonol glycosides, and saccharides. Taste activity values (TAVs) analysis revealed that the key taste components of JH and CG were catechin, epigallocatechin gallate, three theaflavins, caffeine, myrictin-3-O-glucoside, quercetin-3-O-rutinoside, quercetin-3-O-glucoside, quercetin-3-O-galactoside, kaempferol-3-O-rutinoside, kaempferol-3-O-glucoside, and gallic acid. Among the identified compounds, the TAVs of five flavonol glycosides in Ninghong tea were found to be greater than 10 for the first time. This study is helpful to understand the taste quality difference between different grades of Ninghong tea from the molecular sensory level, providing a scientific foundation for quality improvement and targeted regulation.

Withering is one of the major processing steps critical for the quality of black tea. In this study, we investigated the mechanisms underlying the physicochemical changes in metabolites and gene expression during the withering process of black tea using metabolomic and transcriptomic approaches, respectively. Based on gas chromatography/mass spectrometry non-targeted metabolomic approaches (GC-MS) and ultra-high performance liquid chromatograph–tandem mass spectrometry (UHPLC-MS/MS), a total of 76 volatile compounds and 160 non-volatile compounds were identified from tea leaves, respectively. RNA-seq analysis revealed that the number of differentially expressed genes (DEGs) for the comparative combination of withering time (i.e., W4h, W6h, W8h, W10h, and W12h) compared with CK (i.e., fresh leaves) were 3634, 2906, 4127, 5736, and 7650, respectively. The core genes in starch metabolism, namely alpha-amylase (AMY) and beta-amylase (BAM), were upregulated as withering time increased. AMY and BAM contributed to the decomposition of starch to increase the soluble sugars. The content of tea leaf alcohols and aldehydes, which are the vital contributors for greenish aroma, gradually decreased as withering time increased due to the downregulation of associated genes while the compounds related to sweet and fruity characteristics increased due to the upregulated expression of related genes. Most DEGs involved in amino acids were significantly upregulated, leading to the increase in free amino acids content. However, DEGs involved in catechins metabolism were generally downregulated during withering, and resulted in a reduction in catechins content and the accumulation of theaflavins. The same trend was observed in alpha-linolenic acid metabolism-related genes that were downregulated and enhanced the reduction in grassy aroma in black tea. The weighted gene co-expression network analysis (WGCNA) of DEGs showed that one module can be associated with more components and one component can be regulated by various modules. Our findings provide new insights into the quality formation of black tea during the withering process.

Hyperglycemia can cause early damage to human bady and develop into diabates that will severely threaten human healthy. The effectively clinical treatment of hyperglycemiais is by inhibiting the activity of α-amylase. Black tea has been reported to show inhibitory effect on α-amylase and can be used for hyperglycemia treatment. However, the mechanism underlying is unclear. In this study, in vivo experiment showed that black tea theaflavins extract (BTE) effectively alleviated hyperglycemia. In vitro experiment showed that the effects may be caused by the interation between theaflavins and α-amylase. While TF1 and TF3 were mixed type inhibitors of α-amylase, TF2A and TF2B were competitive inhibitors of α-amylase. Molecular docking analysis showed that theaflavins monomers interacted with the hydrophobic region of α-amylase. Further study verified that monomer-α-amylase complex was spontaneously formed depending on hydrophobic interactions. Taken together, theaflavins showed potential anti-hyperglycemia effect via inhibiting α-amylase activity. Our results suggested that theaflavins might be utilized as a new type of α-amylase inhibitor to prevent and cure hyperglycemia.

Aroma plays a pivotal role in the quality of black tea. However, the acceptability of black tea is greatly limited by the green off-flavor (GOF) resulting from the inappropriate processing control. In this study, the key odorants causing GOF were investigated by volatolomics, and their dynamic changes and formation pathways were in-depth understood. Significant alterations in volatile metabolites were observed in the withering stage. A total of 14 key odorants were identified as contributors to GOF, including 2-methylpropanal, 3-methylbutanal, 1-hexanol, nonanal, (E, E)-2,4-heptadienal, benzaldehyde, linalool, (E, E)-3,5-octadiene-2-one, β-cyclocitral, phenylacetaldehyde, (E, E)-2,4-nonadienal, methyl salicylate, geraniol, and β-ionone. Among them, (E, E)-2,4-heptadienal (OAV = 3913), characterized by fatty, green, and oily aromas, was considered to be the most important contributor causing GOF. Moreover, it was found that lipid degradation served as the primary metabolic pathway for GOF. This study provides a theoretical foundation for off-flavor control and quality improvement of black tea.

The sensory quality of black tea (BT) influenced by various factors, among which tree age is particularly significant. People prefer BT produced by fresh leaves from old tea trees, yet the correlation between tree age and tea quality has not been thoroughly investigated. In this study, we analyzed the quality of BT from young trees (H-JYH) and old trees (H-OJYH) using e-tongue technology and sensory evaluation. Our findings revealed that H-OJYH had stronger sweetness and sourness, richer flavor, and diminished bitter-astringency compared to H-JYH. 1231 non-volatile metabolites and 504 volatile metabolites were discovered by ultra-performance liquid chromatography (UPLC) and gas chromatography–mass spectrometry (GC–MS). L-tartaric acid and trans-citridic acid were found to contribute to increase acidity, and 7,8-dihydroxy-6-methoxycoumarin and d-fructose 6-phosphate were associated with enhanced sweetness in H-OJYH. Additionally, lower levels of octyl gallate and vanillic acid in H-OJYH contributed to the diminished bitter-astringency. β-ionone, 2-phenylethanol and phenylacetaldehyde merged as characteristic compounds of older tree BT with stronger floral and sweet aroma. Our study serves as a guideline to explore the relationship between tree age and tea quality.

IntroductionBlack tea, a beverage consumed worldwide, possesses favorable effects on gastrointestinal tract, including nourishing stomach and promoting digestion. Nevertheless, its specific effects on intestinal homeostasis remains inconclusive.MethodsWe applied black tea to mice prior to inducing colitis with DSS and then monitored their body weight and disease activity index (DAI) daily. When sacrificed, we measured intestinal permeability and conducted analyses of mucin and tight junction proteins. We detected inflammatory cytokines, immune cells, and related inflammatory signaling pathways. In addition, the gut microbiota was analyzed through 16S rRNA sequencing, and the concentrations of short-chain fatty acids (SCFAs) were also measured.ResultsThe results showed that black tea-treated group significantly rescued the DSS-disrupted intestinal structure. It reduced the relative abundance of the pathogenic bacterium Turicibacter, while increased the abundance of beneficial bacteria norank_f_Muribaculaceae and restored the contents of SCFAs such as acetate, propionate, and butyrate. It also protected the intestinal barrier by reducing the levels of immune response-related factors (e.g., TNF-α, IL-6, IL-1β) and increasing the expression of tight junction proteins (TJs) (e.g., ZO-1, occludin). Furthermore, black tea exhibited the capacity to suppress the expression of MMP-9 and ICAM-1, as well as to inhibit the activation of NF-κB signaling pathway.DiscussionOur findings provide a theoretical framework that elucidates the mechanisms by which black tea preserves intestinal homeostasis, highlighting its potential as a preventive strategy against intestinal disruptions. This study contributes to the understanding of the dietary effects of black tea on gastrointestinal health.

According to the results of sensory evaluation performed by experts, 14 black tea samples were divided into two groups based on their aroma quality: high-quality and quality-deficient black tea. Using fast gas chromatography-electronic-nose (GC-E-Nose) and gas chromatography-mass spectrometry (GC-MS) combined with multivariate statistical analysis, discriminant analysis of the two groups were carried out, and the key differential components between these groups were selected. The results showed that 117-dimensional dataset was obtained by the fusion of the GC-E-Nose (44-dimensional) and GC-MS (73-dimensional) data and used to establish a model for accurate classification of the two types of black tea employing orthogonal partial least squares-discriminant analysis (OPLS-DA). The model’s explanatory and predictive capacity (R2Y = 0.976, Q2 = 0.959) were better than those of the model established based on the GC-E-Nose or GC-MS data. Based on variable important in projection (VIP) scores > 1.6 and P < 0.05, eight key aroma components including dimethyl sulfide (B3 and B25), β-ionone (A59), (3E)-4,8-dimethylnon-1,3,7-triene (A20), dihydroactinidiolide (A64), linalool (A17), phenylethyl alcohol (A19), δ-octyl lactone (A41) and γ-nonalatone (A45) were selected, which played an important role in the classification. These results showed that GC-E-Nose combined with GC-MS allows rapid and accurate discrimination between quality-deficient and high-quality black tea, which can be used as a supplement to traditional sensory evaluation, providing technical support for quality control and improvement of black tea.

After water, tea is the most popular drink in the world, and its relationship with heart diseases, stroke, and cancer has been always considered by researchers. The aim of the present study is to assess the relationship between green tea or black tea consumption and stroke risk using systematic review and meta-analysis methods. To assess the required resources, PubMed, Scopus, Web of science, Cochrane electronic databases, and the Google Scholar search engine were searched. To assess the study heterogeneity, I2 indexes was used. Data were analyzed using STATA 14 software. P

‘Ming guan’ is a new excellent albino tea variety bred from the descendants of Bai jiguan. In order to explore the quality difference of Ming guan multi tea processing, the fresh leaves of Ming guan were used as raw materials to make the corresponding tea types according to the processing methods of green tea, black tea and white tea, and sensory quality evaluation, aroma and taste analysis were conducted. The results showed that the aroma of Ming guan green tea was tender, floral and fruity, with a mellow taste, the aroma of Ming guan black tea was sweet, floral, with a sweet taste, the aroma of Ming guan white tea was millets, floral, with a fresh taste, and the different processes of Ming guan tea had their own unique floral characteristics. Among the aroma components of Ming guan green tea, terpene aroma components with floral aroma were relatively more abundant, followed by ester aroma components with fruit aroma, which played an important role in the formation of the aroma of Ming guan green tea. The representative aroma components of Ming guan green tea were leaf alcohol ester of foliol caproate, 3-hexenyl caproate, 2-hexenyl caproate, nerolidol, leaf alcohol ester of butyric acid, olivetol and α-farnesene, the representative components of which were mainly esters with fruity aroma and alcohols with floral and fruity aroma, creating the characteristic of Ming guan green tea floral and fruity varieties. The representative components of Ming guan black tea were dihydrolinalool, α-cephalene, β-Ionone, γ-cadinene, methyl hexadecanoic acid and benzaldehyde, which were mainly terpenes and alcohols with floral and sweet aromas, contributing to the floral and sweet aromatic characteristics of Ming guan black tea. The representative components of Ming guan white tea were geraniol, myrcene, 3-carene, linalyl acetate and linalool, and the representative components are mainly alcohols and terpenes with floral aroma. The non-volatile components of Ming guan green tea, Ming guan black tea and Ming guan white tea vary greatly overall. The content of catechins, anthocyanins, some flavonols and flavonoid glycosides (quercetin-3-O-galactoside, quercetin-3-O-glucoside, quercetin-3-O-glucoside 7-O-rhamnoside, etc.) in Ming guan green tea was generally higher than that in Ming guan black tea and Ming guan white tea. The contents of theaflavins, phenolic acids, a few flavonol and flavonoid glycoside compounds (vitexin-2-O-galactoside, vitexin-2-O-rhamnoside, apigenin-6,8-di-C-glucoside, apigenin-6-C-glucoside, etc.) and some amino acid compounds (L-phenylalanine, L-tryptophan, L-isoleucine, L-valine, L-aspartic acid) in Ming guan black tea were higher than those in Ming guan green tea and Ming guan white tea.The content of some amino acid compounds (L-arginine, L-glutamine, L-lysine, L-histidine, L-tyrosine) in Ming guan white tea was higher than that in Ming guan green tea and Ming guan black tea, which may be affected by different processing technologies. This study could provide a theoretical basis for a comprehensive understanding of the chemical basis and quality differences of Ming guan green tea, Ming guan black tea and Ming guan white tea.

Indonesian black tea (BT) waste was utilized as a green corrosion inhibitor for carbon steel (CS) corrosion in a 0.5 M HCl medium. The BT extract was characterized using Fourier transform infra-red. The corrosion inhibition evaluation was studied using conventional weight loss methods, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Further, scanning electron microscopy-energy dispersive X-ray was applied to analyze the surface morphology of pure CS before and after contact with the inhibitor extract. After the addition of inhibitors, CS surface showed a better morphological transformation. The effect of oxygen contamination has also been studied in this research. The corrosion measurements of weight loss, potentiodynamic polarization, and EIS showed that the %IE BT extract was 84.70; 70.00; 72.80% at 0.20 g/L of inhibitor concentration. Adsorption isotherm studies have determined the reaction mechanism between the CS and inhibitor; in which the adsorption follows Langmuir. Gibbs free energy for the three methods is −16.62; −25.34; −24.35 kJ/mol, indicating electrostatic interaction (physisorption) between the metal surface and inhibitor. SEM and focus ion beam show that oxygen contamination can increase the corrosion rate resulting in CS damage. It shows that tea waste products can be used as an alternative corrosion inhibitor.

The biochemistry of human saliva can be altered by food intake. The benefits of tea drinking were extensively studied but the influence of tea ingestion on human saliva has not been revealed. The work aimed to investigate the immediate and delayed effect of vine tea, oolong tea and black tea intake on certain salivary biochemistry and flow rate. The saliva samples of healthy subjects were collected before, after and 30 min after tea ingestion. The chemical compositions and antioxidant capacity of tea samples were analyzed to correlate with salivary parameters. Principal component analysis indicated that the effects of vine tea consumption were dominated by increasing salivary flow rate (SFR), production rate of total protein (TPC), thiol (SH), malondialdehyde, catalase activity and antioxidant capacity (FRAP) in saliva. The antioxidant profile of studied tea samples (FRAP, polyphenols, flavonoids) was positively correlated with salivary SFR, TPC, SH and FRAP but negatively correlated with salivary uric acid concentration in saliva.

Researchers have recently been interested in employing nanoparticles (NPs) obtained from herbal extracts through green synthesis for various applications. This study investigated the detoxification of aflatoxins, which are toxic substances produced by molds Aspergillus flavus and Aspergillus parasiticus. The present work examined the levels of aflatoxins in hazelnut and peanut puree. Turkish black tea extract (BTE), Turkish green tea extract (GTE), green synthesized black tea-based iron oxide nanoparticles (BTFeONPs), and green tea-based iron oxide nanoparticles (GTFeONPs) were produced for aflatoxin removal. Characterizations and various antioxidant and antimicrobial activities of the tea extracts and iron oxide nanoparticles (FeONPs) were investigated. The aflatoxin levels of hazelnut puree used for this study were 6.57 ± 0.06 µg/kg for aflatoxin B1 and 13.03 ± 0.16 µg/kg for total aflatoxin, whereas the aflatoxin levels of (AFLB1) peanut puree were 7.79 ± 0.15 µg/kg for AFLB1 and 15.21 ± 0.12 µg/kg for total aflatoxin. Using soluble BTE resulted in a 40 to 50% decrease in aflatoxin levels in hazelnut and peanut purees, while soluble GTE led to a 30 to 45% decrease. Meanwhile, using BTFeONPs and GTFeONPs resulted in a 33 to 48% and 40 to 50% decrease, respectively, in aflatoxin levels in hazelnut and peanut purees.

Researchers have recently been interested in employing nanoparticles (NPs) obtained from herbal extracts through green synthesis for various applications. This study investigated the detoxification of aflatoxins, which are toxic substances produced by molds Aspergillus flavus and Aspergillus parasiticus. The present work examined the levels of aflatoxins in hazelnut and peanut puree. Turkish black tea extract (BTE), Turkish green tea extract (GTE), green synthesized black tea-based iron oxide nanoparticles (BTFeONPs), and green tea-based iron oxide nanoparticles (GTFeONPs) were produced for aflatoxin removal. Characterizations and various antioxidant and antimicrobial activities of the tea extracts and iron oxide nanoparticles (FeONPs) were investigated. The aflatoxin levels of hazelnut puree used for this study were 6.57 ± 0.06 µg/kg for aflatoxin B1 and 13.03 ± 0.16 µg/kg for total aflatoxin, whereas the aflatoxin levels of (AFLB1) peanut puree were 7.79 ± 0.15 µg/kg for AFLB1 and 15.21 ± 0.12 µg/kg for total aflatoxin. Using soluble BTE resulted in a 40 to 50% decrease in aflatoxin levels in hazelnut and peanut purees, while soluble GTE led to a 30 to 45% decrease. Meanwhile, using BTFeONPs and GTFeONPs resulted in a 33 to 48% and 40 to 50% decrease, respectively, in aflatoxin levels in hazelnut and peanut purees.

Huangjinya has recently seen widespread adoption in key tea-producing areas of China, celebrated for its unique varietal traits. Its leaves are also used to produce black tea with distinctive sensory characteristics. The fragrance-enhancing (EF) process is essential in crafting Huangjinya black tea (HJYBT) and is significant in flavor development. However, the impact of EF on non-volatile metabolites (NVMs), volatile metabolites (VMs), and their interactions remains poorly understood. This study aims to investigate how EF temperatures (60 °C, 70 °C, 80 °C, 90 °C, and 110 °C) influence HJYBT flavor transformation. Quantitative descriptive analysis revealed that EF improved the color, aroma, and appearance of tea leaves. Moreover, after an EF temperature of 80 °C, the HJYBT exhibited lower bitterness and astringency, whereas floral, sweet, and fruity aromas became stronger. However, when EF temperatures exceeded 90 °C, a pronounced burnt aroma developed, with HJYBT at 100 °C exhibiting caramel and roasted notes. Partial least squares discriminant analysis indicated that geraniol and linalool contribute to floral and fruity aromas, while 2-ethyl-6-methyl-pyrazine, furfural, and myrcene are key volatiles for caramel and roast aromas. Heptanal, methyl salicylate, α-citral, 1-hexanol, and (E)-3-hexen-1-ol were found to modify the green and grassy odor. Overall, HJYBT treated at 80 °C EF exhibited the highest umami, sweetness, floral and fruity aromas, and overall taste, exhibiting the least astringency, bitterness, and green and grassy notes. These results provide a significant theoretical basis for enhancing HJYBT quality and selecting the optimal EF method.

Flat black tea (FBT) has been innovatively developed to alleviate homogenisation competition, but the dynamic changes in aroma components during the process remain unclear. This study employed HS-SPME-GC-MS to analyse the aroma components of tea samples from various processing stages of FBT, and to make a comparative assessment with conventional strip-like Congou black tea (SBT). Additionally, a proteomic analysis was conducted on fresh leaves, withered leaves, and frozen–thawed leaves. Significant changes were observed in the aroma components and proteins during the processing. The results of the multivariate and odour activity value analysis demonstrated that the principal aroma components present during the processing of FBT were linalool, (E)-2-hexen-1-al, methyl salicylate, geraniol, hexanal, benzeneacetaldehyde, (Z)-3-hexenyl butyrate, dimethyl sulphide, 2-methylbutanal, 2-ethylfuran, nonanal, nonanol, 3-methylbutanal, (Z)-3-hexen-1-ol, 2-pentylfuran, linalool oxide I, and β-myrcene. Freezing–thawing and final roasting are the key processing steps for forming the aroma quality of FBT. The final roasting yielded a considerable quantity of pyrazines and pyrroles, resulting in a high-fried aroma, but caused a significant reduction in linalool, geraniol, β-myrcene, and esters, which led to a loss of floral and fruity aromas. The freezing–thawing treatment resulted in an accelerated loss of aroma substances, accompanied by a decrease in the expression level of lipoxygenase and 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase. The formation of aroma substances in the linoleic acid metabolic pathway and terpenoid metabolic process was hindered, which had a negative impact on tea aroma. This study elucidates the causes of unsatisfactory aroma quality in tea products made from frozen tea leaves, providing theoretical support for the utilisation of frostbitten tea leaves, and helps us to understand the mechanism of aroma formation in black tea.

Volatile fatty acid derivatives (VFADs) play a significant role in contributing to flowery–fruity flavor black tea. Innovative black tea is typically crafted from aroma-intensive tea cultivars, such as Jinmudan, using defined production methodologies. In this study, the during-processing tea leaves of innovative black tea were applied as materials, and we selected a total of 45 VFADs, comprising 11 derived aldehydes, nine derived alcohols, and 25 derived esters. Furthermore, the dynamic variations of these VFADs were uncovered. Transcriptome analysis was performed to identify genes involved in the LOX (lipoxygenase) pathway, resulting in the identification of 17 CsLOX genes, one hydrogen peroxide lyase (CsHPL) gene, 11 alcohol dehydrogenases (CsADH) genes, 11 genes as acyl CoA oxidase (CsACOX) genes, and three allene oxide synthase (CsAOS) genes. Additionally, the expression levels of these genes were measured, indicating that the processing treatments of innovative black tea, particularly turn-over and fermentation, had a stimulation effect on most genes. Finally, qRT-PCR verification and correlation analysis were conducted to explain the relationship between VFADs and candidate genes. This study aims to provide a reference for illuminating the formation mechanisms of aroma compounds in innovative black tea, thereby inspiring the optimization of innovative processing techniques and enhancing the overall quality of black tea.

Fermentation is a critical process of black tea quality formation and oxygen is the key factor affecting the fermentation, so it is important to analyze the effect of oxygen in fermentation on the quality and metabolites of black tea. One bud and two leaves of 'Longjing 43' tea varieties were used as materials for low oxygen fermentation (5%) , natural fermentation (21%) and oxygen-enriched fermentation (36%) treatments, and the effects of oxygen concentration on sensory quality, non-volatile and volatile metabolites of black tea were analyzed by sensory evaluation combined with gas chromatography-mass spectrometry (GC-MS) and ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS), and the parameters of oxygen-enriched fermentation of black tea were optimized by single factor combined with response surface analysis. Results showed that oxygen-enriched fermentation could significantly improve the taste and aroma quality of black tea compared with nature fermentation (P0.05) in oxygen-enriched fermentation. A total of 25 volatile compounds differed significantly in three treatments, including 12 aldehydes, 2 ketones, 3 alcohols, 3 alkenes, and 5 esters, and the content of most differing compounds increased with increasing oxygen concentration. The optimized parameters of oxygen-enriched black tea were: Oxygen concentration of 40%, oxygenation time of 1.5 h, fermentation time of 4 h. And the contents of TFs, TF, TF3G, TF3'G and TFDG of black tea were 2.86%, 0.25%, 1.71%, 0.24% and 0.68%, respectively. The results of this study would provide an important basis for guiding black tea processing and quality control.

People consume black tea and green tea with certain characteristics in accordance with their wishes and needs. The rating of the product shows the attitude of the people towards a product as well and also reflects their preferences in spending and consuming a product. The aim of this research is to analyse the characteristics of black tea and green tea consumers, to analyse green tea and black tea consumption patterns, and to analyse the components that consideration the preferences of black tea and green tea consumers. Research was held in Southern Purwokerto Sub-district, started from February until March 2020. The number of samples for each black tea and green tea consumers are 50 respondents taken by using multistage random sampling. The analysis which is used is Descriptive Analysis and Factor Analysis. The results show that characteristics of black tea and green tea consumers are women in various range of age. Additionally, married consumers buy black tea and green tea to be consumed together with their family. Perspective of consumption patterns black tea and green tea once a day in the morning breakfast for black tea and in other activities for green tea. The consumption number for family is an average of 50g/months. There are three main components that form preferences on green tea, those are: personality from the tea, identity, and the image of the product. On the other hand, main components that form preferences on black tea are two, those are: image, and identity product.

Abstract Background Systemic fluoride intake is predominantly derived from drinking water and tea. It’s been noted that water and tea containing fluoride, within the boundaries set by the World Health Organization, can lessen the prevalence of dental caries. A review of the literature did not uncover any study that has examined the impact of fluoride in bottled drinking water and tea on enamel of deciduous and permanent teeth. Thus, we assessed the effects of fluoride present in seven different brands of bottled water from distinct geographical regions of Turkey, and a type of tea produced and packaged in Turkey, on the enamel of deciduous and permanent teeth. Materials and methods Fluoride analysis was performed on drinking water sourced from seven different regions of Turkey and a brand of tea brewed with these waters. The tea was harvested and packaged in Turkey. The analysis was conducted using an ion-selective electrode. In total, 112 tooth enamel samples (56 deciduous molars and 56 permanent molars) were randomly divided into eight distinct groups. These were kept in water for 15 min and tea for 15 min every day for a month. The eighth group was treated with fluoride gel prior to tea and water applications. The amount of fluoride in the tooth enamel structure was evaluated using an SEM EDX device before and after the experiment. Results Statistically significant differences were found in fluoride content of enamel between water brands and tooth type (deciduous and permanent teeth). Fluoride levels were higher in the enamel of deciduous teeth than in permanent teeth. Conclusion Regular exposure of enamel samples to black tea and water led to an increase in fluoride levels in the enamel; thus, regular consumption of black tea and fluoride water could help reduce the prevalence of dental caries.

Fermentation is a vital process occurred under the premise of rolling affecting black tea quality. Theoretically, re-rolling during fermentation will remodel the biochemical conditions of tea leaves, and thus influence black tea quality. Herein, we studied the effect of re-rolling on black tea taste and liquor color. Sensory evaluation showed that re-rolling significantly weakened the astringency taste and improved the redness and luminance of liquor. With re-rolling, the color attributes of a* and L* and the contents of theaflavins and thearubigins were significantly improved. Metabolomics analysis showed that the contents of 110 non-volatile compounds were significantly different among black teas with different rolling treatments. In summary, re-rolling accelerated the oxidation of polyphenols into pigments, the hydrolysis of proteins into amino acids, and the metabolism of alkaloids, organic acids, glycosidically-bound volatiles, and lipids during the fermentation period. Our study provided a novel and simple way to improve black tea quality.

The present study comprehensively used integrated multi-spectral omics combined with sensory evaluation analysis to investigate the quality of three types of Yunnan Congou black teas from different tree ages (decades, DB; hundreds, HB; a thousand years, TB). TB infusion presented the highest scores of sweetness and umami, higher brightness, and yellow hue. Eighty-four marker metabolites were identified, including Amadori rearrangement products, catechin oxidation products, flavonoid glycosides, and organic acids, which are simultaneously related to tea infusions' color and taste. Moreover, the content of some characteristic flavonoid glycosides and organic acids was determined. Our finding implied trans-4-O-p-coumaroylquinic acid and quercetin 3-O-rutinoside contributed to bitterness and astringency, while dehydro theanine-glucose Amadori product and xylopyranosyl-glucopyranose resulted in umami and sweetness. These results provided quantitative and qualitative information for deciphering differences among black teas with different tea plant ages, conducing to the further utilization of ancient tea plants in Southwest China.

In Sri Lanka, several tea grades are produced in factories located in different agro-climatic regions within three geographical elevations. The study aimed to determine the microbial quality of different tea grades and composite tea samples obtained from factories situated at diverse locations. The average APC, yeast & mould counts and coliforms in different tea grades ranged from 3.4 × 103 to 2.0 × 104 cfu/g, 4.8 × 102 to 2.5 × 103 cfu/g and 0.005 to 3.9 × 101 Most Probable Number (MPN)/g respectively. The tea samples collected from different factories had mean values of APC and yeast & mould as 5.3 × 103±1.3 × 103 cfu/g and 9.7 × 102±1.9 × 102 cfu/g. Escherichia coli (E.coli) and Salmonella were not detected either in tea grades or in composite samples. The identified microorganisms in tea samples belong to phyla Firmicutes, Proteobacteria, Ascomycota, Basidiomycota and Zygomycota.The samples collected from the mid country elevation had the highest counts of APC and yeast & mould counts were high in the low country elevation. More than 70 % of the tested samples comply with the SLTB guidelines given for the microbiological quality of black tea. The distribution of bacterial, yeast and mould and coliform densities of tea were significantly variable with respect to geographic areas.

Black tea was a drink made through fermentation by the enzyme polyphenol oxidase which could enzymatically oxidize catechins in fresh leaves. Lemon juice was added to the tea to determine the effect of adding lemon juice to the tea. This research aimed to determine the effect of brewing temperature and the pro-oxidant properties of adding lemon juice on changes in polyphenols and antioxidant activity of black tea. This research used a factorial design with 2 treatment factors, namely black tea brewed at 80oC and 100oC with the addition of 0%, 1% and 2% lemon juice with 3 repetitions. Green tea was used as a control. Analysis was carried out on total phenol content and IC50. Data analysis used the ANOVA test with a confidence level of 0.05. The research results showed that the total phenol of steeping black tea at a temperature of 80oC were lower than those steeping black tea at a temperature of 100oC, namely 20.41% and 27.08% respectively, but lower than the total phenol of green tea. Likewise, the higher level of added lemon juice, the higher total phenol content, but lower than total phenol content of green tea. For antioxidant activity was measured by IC50 inhibition, it showed that IC50 value at a black tea steeping temperature of 100oC was lower than IC50 value at 80oC black tea steeping. Likewise, with the addition of lemon juice, IC50 value decreased, namely 65.75 µg/ml to 35.84 µg/ml for steeping black tea at 80oC and 22.88 µg/ml to 15.94 µg/ml for steeping black tea at 100oC. The smaller IC50 value, the higher antioxidant activity.

Tea polyphenol, a vital indicator used for the detection of tea quality, is of great significance to quickly detect the tea polyphenol content via near infrared spectroscopy. In this paper, the near infrared spectroscopy in combination with partial least squares (PLS) was adopted to establish the rapid analysis models by near infrared for tea polyphenol content of powdered and complete tea samples respectively, using 144 black tea samples as the study objects, revealing that the prediction model established by SNV+first derivative+Savitzky-Golay smoothing combined with PLS had the optimal effect in the results. The correlation coefficient (r) was 0.9990 and the root mean square error of calibration (RMSEC) was 0.165% of the training set, while the r was 0.9243 and the root mean square error of prediction (RMSEP) was 0.972% of the prediction set in powered tea samples. At the same time, the r was 0.9967 and the RMSEC was 0.310% of the training set, while the r was 0.9541 and the RMSEP was 0.870% of the prediction set in complete tea samples. The results showed that the PLS model for complete tea samples was better than that for powdered tea. Therefore, rapid and nondestructive detection of tea polyphenols in black tea can be achieved by near infrared spectroscopy.

In diabetes mellitus, disordered glucose and lipid metabolisms precipitate diverse complications, including nonalcoholic fatty liver disease, contributing to a rising global mortality rate. Theaflavins (TFs) can improve disorders of glycolipid metabolism in diabetic patients and reduce various types of damage, including glucotoxicity, lipotoxicity, and other associated secondary adverse effects. TFs exert effects to lower blood glucose and lipids levels, partly by regulating digestive enzyme activities, activation of OATP-MCT pathway and increasing secretion of incretins such as GIP. By the Ca2+-CaMKK ꞵ-AMPK and PI3K-AKT pathway, TFs promote glucose utilization and inhibit endogenous glucose production. Along with the regulation of energy metabolism by AMPK-SIRT1 pathway, TFs enhance fatty acids oxidation and reduce de novo lipogenesis. As such, the administration of TFs holds significant promise for both the prevention and amelioration of diabetes mellitus.

(1) Objectives: Traditional kombucha (K) is a fermented beverage obtained from black or green tea infusion. Besides traditional substrates, the possibility of using alternative ingredients resulted in changes in metabolic profile and biological activity. The aim of this work was to study an alternative kombucha (KJ) prepared by the addition of jujube powder to black tea. (2) Materials and Methods: Changes in pH, protein, sugars, phenolic (TPC), flavonoid (TFC), and vitamin C and B12 content were evaluated at different time points over a period of 45 days. The identification of polyphenols by HPLC DAD and the antioxidant capacity by DPPH, ABTS, and FRAP tests of all samples was also carried out. (3) Results: The results showed higher protein, total phenolic content, and antioxidant capacity in KJ samples than in K ones. Vitamin C content increased during fermentation and reached its maximum concentration on day 45 (7.1 ± 0.3 mg/100 mL) for KJ. Caffeine in the supplemented samples was the main biocompound among those identified. Vitamin B12 formed on day 4 in K and after 24 h in KJ samples, remaining constant at the initial value of 2.30 ± 0.01 mg/100 mL up to day 45. (4) Conclusions: The results highlight that the fortification of kombucha with jujubes improved its biological activity and the content of bioactive compounds.

The bioactivity of tea polysaccharides (TPs) has been widely reported, but studies to date have focused on green tea. Some human health investigations have implied that black tea may possess potential antidiabetic effects, but less is known about their potential role and related antidiabetic mechanism. The present study was, therefore, conducted to investigate the chemical properties and antidiabetic activity of TPs from black tea. Monosaccharide composition revealed that Alduronic acid (77.8 mol%) considerably predominated in the fraction. TP conformation analysis indicated that three components in TPs were all typical of high-branching structures. Oral administration of TPs could effectively alleviate fasting blood glucose in type 2 diabetes mellitus (T2D) mice, with the values 23.6 ± 1.42, 19.6 ± 2.25, and 16.4 ± 2.07 mmol/L in the 200, 400, and 800 mg/kg·BW groups, respectively. Among these TPs groups, the 800 mg/kg·BW groups significantly decreased by 37.88% when compared with the T2D+water group (p < 0.05). Further studies demonstrated that TP treatment upregulated the expression of p-Akt/p-PI3K (p < 0.001). Additionally, TP treatment significantly promoted glucose transporter protein 2 (GLUT2) translocation in the liver (p < 0.001). These findings suggest that TPs from black tea protect against T2D by activating PI3K/Akt/GLUT2 signaling and might serve as a novel therapeutic candidate for T2D.

Gas chromatography–ion mobility spectrometry (GC-IMS) is a smart method that has been applied to determine the volatile compounds in Chinese teas, but its use in comparing the volatile compounds of different types of tea has not been mentioned. In this study, the volatile compounds found in four types of samples (green, yellow, white, and black teas) made with fresh leaves of Camellia sinensis (L.) Kuntze ‘Zhongcha 111’ were analyzed using GC-IMS. The results showed that 93 volatile compounds were identified from our tea samples and that the average volume of aldehydes was higher than that for other compounds, especially in white tea. The different samples were successfully categorized using multivariate statistical analysis. Using partial least squares discriminant analysis (PLS-DA), we found 15 key compounds, including four differential components: (E)-2-hexenal, 2-furanmethanethio, 2-hexanol, and 1-octene. There were 29 common components, and their total content reached 386.0 μg/g. Moreover, the 3-methyl-2-butenal and dimethyl disulfide detected in the four samples were also differential compounds, varying according to the manufacturing technology. Thus, this study demonstrates that different types of teas can be discriminated easily using GC-IMS and that this is helpful to shorten the time for improving tea quality and developing new products.

In this study, the influence of different tea extract substrates on the biological activities of kombucha beverages was investigated. The variations in bioactive compounds such as polyphenols and flavonoids and their potential health-promoting properties represented by antioxidant activity were analyzed. Our findings shed light on the diverse effects of tea substrates on the production of bioactive compounds and their subsequent impact on the biological activities of kombucha, providing valuable insights for optimizing kombucha production and its potential health benefits. The new tea substrate for kombucha, called horchata, an Ecuadorian tea, shows a similar trend but with a low content of phenolics (4.511 ± 0.111 mg gallic acid equivalent (GAE)/g dry weight (DW)) and flavonoids (1.902 ± 0.0455 mg quercetin equivalent (QE)/g DW), and antioxidant activity (DPPH—33.569 ± 1.377 µmol TROLOX/g DW, ABTS—20.898 ± 2.709 µmol TROLOX/g DW, FRAP—34.456 ± 2.0618 Fe2+ mM/100 g DW compared to black and green tea as substrates for kombucha. Through HPLC-DAD, several polyphenols were registered, and homovanillic acid showed the highest concentration (74.45 mg/100 g). Horchata kombucha scored the highest in sweetness and smell, reflecting its popularity among the tasters, making it a valuable candidate as a kombucha substrate.

Tea is central to the culture and economy of the Middle East countries, especially in Iran. At some levels of society, it has become one of the main food items consumed by households. Bioactive compounds in tea, known for their antioxidant and anti-inflammatory properties, have proven to confer neuroprotective effects, potentially mitigating diseases such as Parkinson’s, Alzheimer’s, and depression. However, the popularity of black tea has also made it a target for fraud, including the mixing of genuine tea with foreign substitutes, expired batches, or lower quality leaves to boost profits. This paper presents a novel approach to identifying counterfeit Iranian black tea and quantifying adulteration with tea waste. We employed five deep learning classifiers—RegNetY, MobileNet V3, EfficientNet V2, ShuffleNet V2, and Swin V2T—to analyze tea samples categorized into four classes, ranging from pure tea to 100% waste. The classifiers, tested in both patched and non-patched formats, achieved high accuracy, with the patched MobileNet V3 model reaching an accuracy of 95% and the non-patched EfficientNet V2 model achieving 90.6%. These results demonstrate the potential of image processing and deep learning techniques in combating tea fraud and ensuring product integrity in the tea industry.

As a non-destructive, fast, and cost-effective technique, near-infrared (NIR) spectroscopy has been widely used to determine the content of bioactive components in tea. However, due to the similar chemical structures of various catechins in black tea, the NIR spectra of black tea severely overlap in certain bands, causing nonlinear relationships and reducing analytical accuracy. In addition, the number of NIR spectral wavelengths is much larger than that of the modeled samples, and the small-sample learning problem is rather typical. These issues make the use of NIRS to simultaneously determine black tea catechins challenging. To address the above problems, this study innovatively proposed a wavelength selection algorithm based on feature interval combination sensitivity segmentation (FIC-SS). This algorithm extracts wavelengths at both coarse-grained and fine-grained levels, achieving higher accuracy and stability in feature wavelength extraction. On this basis, the study built four simultaneous prediction models for catechins based on extreme learning machines (ELMs), utilizing their powerful nonlinear learning ability and simple model structure to achieve simultaneous and accurate prediction of catechins. The experimental results showed that for the full spectrum, the ELM model has better prediction performance than the partial least squares model for epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG). For the feature wavelengths, our proposed FIC-SS-ELM model enjoys higher prediction performance than ELM models based on other wavelength selection algorithms; it can simultaneously and accurately predict the content of EC (Rp2 = 0.91, RMSEP = 0.019), ECG (Rp2 = 0.96, RMSEP = 0.11), EGC (Rp2 = 0.97, RMSEP = 0.15), and EGCG (Rp2 = 0.97, RMSEP = 0.35) in black tea. The results of this study provide a new method for the quantitative determination of the bioactive components of black tea.

Lipids are important tea aroma precursors. Due to the complexity of black tea processing involving both enzymatic and thermal reactions, the role of lipids in black tea aroma formation remained unclear. Herein, the dynamic changes of lipids and volatiles during black tea processing were simultaneously analyzed by lipidomics and volatolomics using ultra-high-performance liquid chromatography coupled to Q-Exactive Orbitrap mass spectrometry (UHPLC-Q-Exactive) and gas chromatography-tandem mass spectrometry (GC-MS/MS). The lipidomics method was validated in linearity, reproducibility, and recovery, which showed a high reliability. A total of 374 lipids and 88 volatiles were detected. Among them, 362 lipids and 29 fatty acid-derived volatiles (FADVs) were significantly altered depending on different processing stages. During the enzyme-driven stages of black tea processing (withering, rolling and fermentation), monogalactosyldiacylglycerol (MGDG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE) were largely downregulated (

AbstractDifferent applications of the fertilizers were carried out to study their effect on tea plant productivity and phytochemicals in prepared black tea. Weight and dimensions of the bud, first and second leaf of each variety was taken for this purpose. Organic application (T1) 200 g vermicomposting per bush and inorganic application (T2) which is a combination of 2.5 g urea, 5 g Di-ammonium phosphate and 1 g potash was applied per bush. Weights of the bud was found higher in organic treated Ambari (0.061 g), Phubtsering 312 (0.056 g), Takda 78 (0.069 g) but in Banekbern 157 (0.046 g) and Gumti (0.07 g) inorganic fertilizer treatment increased the weight. The weight of first leaves ranged from 0.04 g to 0.115 g for the experimental samples. The weight of first leaves of PB 312, Banekbern 157 and Gumti varieties was observed to have greater for inorganic while for AV2 and Takda 78 weight of first leaf was observed to be greater for organic treatment. The weight of second leaf was found greater for inorganic treatment for all varieties which ranged from 0.115 g to 0.335 g in all samples of tea. In all varieties length was found to be increased in inorganic treatments. In all varieties, inorganic practice has positive effect in the growth and yield of the leaves. The fresh leaves and black tea prepared from the leaves of organic treatments had better tea quality in reference to TPC, TFC and DPPH radical scavenging activity. The caffeine content was not significantly different (p > 0.05) for the organic and inorganic treatment for both fresh leaves and prepared tea. Black tea prepared by organic treated leaves from Gumti and AV2 were superior to other samples regarding the phytochemical properties. Inorganic treatments increased the yield and growth but the quality of tea was increased by organic fertilizers.

Due to its traditional fermentation, there are obvious limits on the quality improvements in black tea. However, microbial fermentation can provide an abundance of metabolites and improve the flavor of tea. The “golden flower” fungi are widely used in the microbial fermentation of tea and has unique uses in healthcare. To further explore the improvements in black tea quality achieved via microbial fermentation, we used widely targeted metabolomics and metagenomics analyses to investigate the changes in and effects of metabolites and other microorganisms during the interaction between the “golden flower” fungi and black tea. Five key flavor metabolites were detected, the levels of catechin, epigallocatechin gallate, (−)-epicatechin gallate were decreased by different degrees after the inoculation of the “golden flower” fungus, whereas the levels of caffeine and (+)-gallocatechin increased. Botryosphaeriaceae, Botryosphaeriales, Dothideomycetes, Aspergillaceae, Trichocomaceae, and Lecanoromycetes play a positive role in the black tea fermentation process after inoculation with the “golden flower” fungi. D-Ribose can prevent hypoxia-induced apoptosis in cardiac cells, and it shows a strong correlation with Botryosphaeriaceae and Botryosphaeriales. The interaction between microorganisms and metabolites is manifested in tryptophan metabolism, starch and sucrose metabolism, and amino sugar and nucleotide sugar metabolism. In conclusion, the changes in metabolites observed during the fermentation of black tea by “golden flower” fungi are beneficial to human health. This conclusion extends the knowledge of the interaction between the “golden flower” fungi and black tea, and it provides important information for improving the quality of black tea.

Rolling represents an essential stage in congou black tea processing. However, the influence of rolling pressure on tea flavor and non-volatile compounds remains unclear. Herein, a combination of untargeted metabolomics, tea pigments quantification, E-tongue, colorimeter and sensory evaluation was used to evaluate the effect of rolling pressure on black tea quality. As the rolling pressure increased, theaflavins (TFs), thearubigins (TRs), and theabrownins (TBs) significantly elevated. The tea metabolic profiles fluctuated and 47 metabolites were identified as key differential metabolites including flavan-3-ols, flavonol/flavone glycosides, phenolic acids, amino acids. These substances altered possibly due to the variations in enzymatic oxidation of tea phenolics and amino acids. Overall, black tea with moderate rolling pressure presented higher sweetness, lower bitterness, and higher quality index (10 TFs + TRs)/TBs. The results were verified by a validation batch. This study provided new insights into the regulation of rolling pressure and a guidance for black tea processing.

The reasons for the change in volatile metabolites and aroma of black tea during storage remain unclear. Therefore, we used HS-SPME and GC–MS methods to analyze the aroma compounds of new tea (2021) versus aged tea groups (2015, 2017, and 2019). A total of 109 volatile components were identified. During storage, 36 metabolites mainly with floral and fruity aromas decreased significantly, while 18 volatile components with spicy, sour, and woody aromas increased significantly. Linalool and beta-ionone mainly contributed to sweet and floral aromas of freshly-processed and aged black tea, respectively. Isovaleric acid and hexanoic acid mainly caused sour odor of aged black tea. The monoterpene biosynthesis and secondary metabolic biosynthesis pathways might be key metabolic pathways leading to changes in the relative content of metabolites during storage of black tea. Our study provides theoretical support for fully understanding the changes in the aroma quality of black tea during storage.

Shaking is an innovative technology employed in black tea processing to enhance flavor. However, the effects of shaking on the evolutionary mechanisms of volatile metabolites (VMs) remain unclear. In this study, we compared the effects of a shaking–withering method with those of traditional withering on the flavor and VMs transformation of black tea. The results showed that black tea treated with shaking exhibited excellent quality with floral and fruity aroma. Based on gas chromatography-tandem mass spectrometry, 128 VMs (eight categories) were detected. Combining variable importance projection with odor activity value analysis, eight key differential VMs were identified. Shaking could promote the oxidative degradation of fatty acids and carotenoids and modulate the biosynthesis of terpenoids to facilitate the formation of floral/fruity VMs (such as (Z)-hexanoic acid-3-hexenyl ester, ethyl hexanoate, trans-β-ionone, and decanal). Our findings provide theoretical guidance for the production of high-quality black tea with floral and fruity aromas.