The Potential Use of Near Infrared Spectroscopy (NIRS) to Determine the Heavy Metals and the Percentage of Blends in Tea

The following study analyzed the potential of Near Infrared Spectroscopy (NIRS) to predict the metal composition (Al, Pb, As, Hg and Cu) of tea and for establishing discriminant models for pure teas (green, red, and black) and their different blends. A total of 322 samples of pure black, red, and green teas and binary blends were analyzed. The results showed that pure red teas had the highest content of As and Pb, green teas were the only ones containing Hg, and black teas showed higher levels of Cu. NIRS allowed to predict the content of Al, Pb, As, Hg, and Cu with ratio performance deviation values > 3 for all of them. Additionally, it was possible to discriminate pure samples from their respective blends with an accuracy of 98.3% in calibration and 92.3% in validation. However, when the samples were discriminated according to the percentage of blending (>95%, 95-85%, 85-75%, or 75-50% of pure tea) 100% of the samples of 10 out of 12 groups were correctly classified in calibration, but only the groups with a level of pure tea of >95% showed 100% of the samples as being correctly classified as to validation.

Non-Targeted Metabolomics Reveals the Effects of Different Rolling Methods on Black Tea Quality

A non-targeted metabolomics approach and sensory evaluation, coupled with multivariate statistical analysis, systematically uncover the impact of the rolling time on the quality parameters of black tea. GC-MS analysis reveals that a moderate extension of rolling time favorably contributes to the accumulation of characteristic aroma components in black tea. The volatile components reach their highest concentration in black tea samples processed during an 80-min rolling period. UHPLC-Q-TOF/MS analysis demonstrates a substantial decrease in the contents of catechins and flavonoids with an increase in rolling time. Simultaneously, the production of theaflavins, coupled with the degradation of green bitterness volatiles (GBVs), significantly contributes to the formation of endogenous aroma components in black tea. These findings underscore the close relationship between rolling time control and black tea quality, emphasizing that a moderate extension of the rolling time fosters the development of improved black tea flavor quality. The comprehensive quality evaluation indicates that the optimal duration is 80 min. However, the initial 0 to 20 min of rolling is a crucial phase for the genesis and transformation of black tea quality. This study offers valuable insights into the influence of rolling time on black tea quality, potentially enhancing future studies of rolling technology. It provides theoretical guidelines for optimizing the processing of Gongfu black tea.

Determination of C═C Positions of Unsaturated Fatty Acids in Foods via Ambient Reactive Desorption Ionization with Water Dimer Radical Cations

The positions of C═C bonds in unsaturated fatty acids (FAs) are one of the main factors determining the quality of food flavor. Herein, we developed an approach for the determination of C═C bonds of FAs by online epoxidation reaction with water dimer radical cations. The limit of detection for octenoic acid isomers was ∼9 μg/L. The positions of C═C bonds in trans-2/3-hexenoic acid, trans-2/3-octenoic acid, oleic acid, linoleic acid, and linolenic acid in black tea or olive oil samples were directly determined by the established method. These results indicate that the established method allows the rapid determination of unsaturated FAs in black tea and olive oil. The advantages of this approach include the analysis speed (∼1 min per sample), simple device, and no need for complex pretreatment. This study not only provides a strategy for the determination of C═C positions but also offers new possibilities for applications in the field of food chemistry.

[Dynamic Chemistry of Tannins]

Tannins are a group of polyphenols that possess the ability to precipitate proteins, causing an undesirable astringent taste by interacting with salivary peptides. This interaction deactivates the digestive enzymes; therefore, tannins are considered as plant defense substances. The health benefits of tannins and related polyphenols in foods and beverages have been demonstrated by biological and epidemiological studies; however, their metabolism in living plants and the chemical changes observed during processing of foods and medicinal herbs raises some questions. This review summarizes our studies concerning dynamic changes observed in tannins. Ellagitannins present in the young leaves of Camellia japonica and Quercus glauca undergo oxidative degradation as the leaves mature. Similar oxidative degradation is also observed in whiskey when it is kept for aging in oak barrels, and in decaying wood caused by fungi in natural forests. In contrast, ellagitannins have been observed to undergo reduction in the leaves of Carpinus, Castanopsis, and Triadica species as the leaves mature. This phenomenon of reductive metabolism in leaves enabled us to propose a new biosynthetic pathway for the most fundamental ellagitannin acyl groups, which was also supported by biomimetic synthetic studies. Polyphenols undergo dynamic changes during the process of food processing. Catechin in tea leaves undergo oxidation upon mechanical crushing to generate black tea polyphenols. Though detailed production mechanisms of catechin dimers have been elucidated, structures of thearubigins (TRs), which are complex mixtures of oligomers, remain ambiguous. Our recent studies suggested that catechin B-ring quinones couple with catechin A-rings during the process of oligomerization.

Transcriptome and proteomics conjoint analysis reveal anti-alcoholic liver injury effect of Dianhong Black Tea volatile substances

Dianhong Black Tea, a fermented tea containing various bioactive ingredients, has been found to have a significant role in alleviating alcoholic liver injury (ALI). One of its main unique components, Dianhong Black Tea volatile substances (DBTVS), may have potential anti-ALI effects. However, its effects and underlying molecular mechanisms are still unknown. In this study, we aimed to investigate the potential of DBTVS as an anti-ALI agent using alcohol-fed rats. We assessed the effect of DBTVS on ALI by analyzing serum transaminase and lipid levels, as well as conducting hematoxylin-eosin and oil red O staining. Additionally, GC-MS was used to detect the components of DBTVS, while transcriptome, proteomics analysis, Western blot, and molecular docking were employed to uncover the underlying mechanisms. Our results demonstrated that DBTVS significantly reduced serum ALT and AST levels and improved lipid metabolism disorders. Moreover, we identified 14 components in DBTVS, with five of them exhibiting strong binding affinity with key proteins. These findings suggested that DBTVS could be a promising agent for the prevention and treatment of ALI. Its potential therapeutic effects may be attributed to its ability to regulate lipid metabolism through the PPAR signaling pathway.

Characterization of phenolic components of black teas of different origins and the effect of brewing duration on quality properties

This research aims to identify the phytochemical constituents of 79 different samples of black tea, including varieties from India, Iran (IrT), Turkey (TT), and Sri Lanka. In addition, this study investigates the effect of varying brewing times on the quality characteristics of tea. Therefore, we analyzed the phytochemical content of tea using a novel LC-MS/MS method that we developed, which identifies 53 different phenolic compounds. Furthermore, objective evaluations were conducted on the total phenolic compound, total flavonoid compound, antioxidant activity, and color values at 15, 30, and 60-min brewing intervals. The prevailing phenolic compounds discovered in the corresponding tea classifications were quantitatively analyzed to be quinic acid, epicatechin gallate, epigallocatechin gallate, epicatechin, epigallocatechin, gallic acid, nicotiflorine, and isoquercitrin. The study found that the TT and IrT groups had the richest phytochemical content and the highest antioxidant activity. The Turkish tea group had the highest measurement for the desired red color, which is considered a sensory property. Infusion color, antioxidant activity, and total phenolic and flavonoid contents showed significant increases with prolonged brewing time. It was important to note that the chemical composition of tea varies according to its origin and brewing conditions. Extending the brewing time improved the quality of the tea. It should be noted, however, that longer brewing times result in a more intense release of flavonoids, and this increase may have a pro-oxidant effect.

Comparison of Volatile and Nonvolatile Metabolites in Black Tea under Four Second-Drying Methods Using Widely Targeted Metabolomics

Second-drying has an impact on the development of flavor and aroma in black tea. However, the effect of the shape changes of the tea leaves during second-drying on the quality of black tea has yet to be evaluated. In this study, GC-TOFMS and UPLC-HRMS identified 411 volatile metabolites and 253 nonvolatile metabolites. Additionally, 107 nonvolatile compounds and 21 different volatiles were screened. Significant alterations (p < 0.01) were found in 18 amino acid derivatives, 17 carbohydrates, 20 catechins, 19 flavonoids, 13 phenolic acids, and 4 organic acids. The content of certain amino acids and carbohydrates correlated with the shape of black tea. Furthermore, sweet aroma compound formation was facilitated by hot-air second-drying while the remaining second-drying approaches encouraged the formation of the fruity aroma compound. The results of the study provide a theoretical basis and technical instructions for the accurate and precise processing of premium black tea.

Fermented Tea as a Food with Functional Value-Its Microbiological Profile, Antioxidant Potential and Phytochemical Composition

Kombucha is a fermented tea drink produced by a symbiotic culture of bacteria and yeast, known as SCOBY. Its base has traditionally been black tea, which has been recognized for its health-promoting properties, particularly its antioxidant activity based on its high content of pol-yphenolic compounds. A number of previous studies have demonstrated the equally favourable biochemical and phytochemical composition of green tea. The aim of this study was to analyse and compare the basic biochemical composition, microbiological composition and antioxidant properties of black and green tea-based Kombucha. The green tea-based Kombucha showed a quantitatively more abundant microbial composition (Lactic Acid Bacteria, Acetobacter sp., Yeast), a higher reducing potential (FRAP-4326.58 Fe(II)µM/L) and a higher content of total polyphenols (23.84 mg GAE/100 mL, reducing sugars (3212.00 mg/100 mL) as well as free amino acids (849.00 mg GLY/mL). Kombucha made from black tea, on the other hand, showed a higher anti-oxidant potential (1.17 Trolox (mM) TEAC), neutralising the DPPH radical at 94.33% and ABTS at 97.74%. It also had a higher level of acetic acid (0.08 g/100 mL). Green tea kombucha had a higher scavenging capacity of 90.6% for superoxide radical (O2-) and 69.28% for hydroxyl radical (·OH) than black tea kombucha. In the present study, both kombucha drinks tested were shown to be source of potent antioxidants. In addition, green tea, as a kombucha base, has proven to be as beneficial a raw material that will provide full nutritional and health-promoting values as traditional kombucha.

Tea Harvesting and Processing Techniques and Its Effect on Phytochemical Profile and Final Quality of Black Tea: A Review

Tea (Camellia sinensis) has grown for over 300 years and is recognized worldwide as among other well-renowned crops. The quality of black tea depends on plucking (method, standard, season, and intervals), withering and rolling (time and temperature), fermentation (time, temperature, and RH), drying (temperature and method), and storage conditions, which have a high influence on the final quality of black tea. At the rolling stage, the oxidation process is initiated and ends at the early drying stage until the enzymes that transform tea polyphenols into thearubigins (TRs) and theaflavins (TFs) are denatured by heat. By increasing fermentation time, TRs increased, and TF decreased. Each is liable for black tea's brightness, taste, and color. The amino acids and essential oils also grant a distinctive taste and aroma to black tea. Throughout withering, rolling, and fermentation, increases were found in essential oil content, but during drying, a decrease was observed. However, the Maillard reaction, which occurs when amino acids react with sugar during drying, reimburses for this decrease and enhances the flavor and color of black tea. As compared to normal conditions, accelerated storage showed a slight decrease in the total color, TF, and TRs. It is concluded that including plucking, each processing step (adopted technique) and storage system has a remarkable impact on black tea's final quality. To maintain the quality, an advanced mechanism is needed to optimize such factors to produce high-quality black tea, and an objective setting technique should be devised to attain the desirable quality characteristics.

Metabolic improvements of novel microbial fermentation on black tea by Eurotium cristatum

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.

Difference in Aroma Components of Black Teas Processed on Different Dates in the Spring Season

Tea aroma greatly varies with the production date. This study investigated the aroma differences among black teas processed on different dates (March 23rd, April 8th, April 15th, April 27th, and May 7th) in the spring. A sensory evaluation showed that the black tea produced on April 15th had a strong and lasting sweet aroma and the highest score of 93.5. In total, 71 volatile compounds were identified, and alcohols were the predominant category, accounting for 60.98%. From March 23rd to May 7th, the total content of volatile compounds showed a parabolic change trend and reached its maximum on April 15th (715.27 μg/L); the flavor index first peaked on April 8th (23.25) and then gradually decreased. A multivariate statistical analysis showed that 39 volatile compounds were important, differential aroma components. An odor activity value (OAV) analysis showed that the predominant odorants were β-ionone, β-damascenone, linalool, (E)-β-ocimene, and geraniol, all with values larger than 100. The total OAVs of undesirable odorants decreased and reached their minimum (70.4) on April 27th, while the total OAVs of pleasant odorants and the ratio of pleasant/undesirable odorants showed inverse changes and reached their maximum (2182.1 and 31.0, respectively) on April 27th. Based on the significance of differences and OAVs, linalool, (E)-β-ocimene, geraniol, and (E,E)-2,4-nonadienal were considered as the key differential odorants. Combined with the sensory evaluation and the differences in aroma components, it was proposed that black teas produced around April 15th in the Hunan district are more likely to have a strong and lasting sweet aroma. This study will provide scientific guidance for the production of black tea in the Hunan district, China.

Comparison of Si-GA-PLS and Si-CARS-PLS build algorithms for quantitation of total polyphenols in black tea using the spectral analytical system

BACKGROUND

The objective of the current study was to compare two machine learning approaches for the quantification of total polyphenols by choosing the optimal spectral intervals utilizing the synergy interval partial least squares (Si-PLS) model. To increase the resilience of built models, the genetic algorithm (GA) and competitive adaptive reweighted sampling (CARS) were applied to a subset of variables.

RESULTS

The collected spectral data were divided into 19 sub-interval selections totaling 246 variables, yielding the lowest root mean square error of cross-validation (RMSECV). The performance of the model was evaluated using the correlation coefficient for calibration (RC ), prediction (RP ), RMSECV, root mean square error of prediction (RMSEP) and residual predictive deviation (RPD) value. The Si-GA-PLS model produced the following results: PCs = 9; RC  = 0.915; RMSECV = 1.39; RP  = 0.8878; RMSEP = 1.62; and RPD = 2.32. The performance of the Si-CARS-PLS model was noted to be best at PCs = 10, while RC  = 0.9723, RMSECV = 0.81, RP  = 0.9114, RMSEP = 1.45 and RPD = 2.59.

CONCLUSION

The build model's prediction ability was amended in the order PLS < Si-PLS < CARS-PLS when full spectroscopic data were used and Si-PLS < Si-GA-PLS < Si-CARS-PLS when interval selection was performed with the Si-PLS model. Finally, the developed method was successfully used to quantify total polyphenols in tea. © 2023 Society of Chemical Industry.

Oligomerization Mechanisms of Tea Catechins Involved in the Production of Black Tea Thearubigins

Thearubigins (TRs) are chemically ill-defined black tea pigments composed of numerous catechin oxidation products. TRs contain oligomeric components; however, the oligomerization mechanisms are poorly understood. The comparison of the 13C nuclear magnetic resonance (NMR) spectra of TRs with different molecular sizes suggested the participation of A-ring methine carbons in the oligomerization. Crushing fresh tea leaves with phloroglucinol, a mimic of the catechin A-rings, yielded the phloroglucinol adducts of the B-ring quinones of pyrogallol-type catechins and dehydrotheasinensins, indicating that intermolecular oxidative couplings between pyrogallol-type B-rings and A-rings are involved in the oligomerization. This is supported by the comparison of the 13C NMR spectra of the oligomers generated from the dehydrotheasinensins and epicatechin. Furthermore, the presence of the quinones or related structures in the catechin oligomers is shown by condensation with 1,2-phenylenediamine. The pyrogallol-type catechins account for approximately 70% of tea catechins; therefore, the B-A ring couplings of the pyrogallol-type catechins are important in the catechin oligomerization involved in TR production.

Re-Rolling Treatment in the Fermentation Process Improves the Aroma Quality of Black Tea

Aroma is a vital factor influencing tea quality and value. It is a challenge to produce a kind of black tea with a floral/fruity aroma, good taste, and without a green/grassy odor simultaneously using small- and medium-leaf tea species. In this study, the effect of re-rolling treatment on the aroma quality of small-leaf Congou black tea was investigated using the methods of the equivalent quantification of aroma and gas chromatography-mass spectrometry (GC-MS). Sensory evaluation showed that re-rolling treatment improved the aroma quality of Congou black tea by conferring upon it floral and fruity scents. In total, 179 volatile compounds were identified using GC-MS, of which 97 volatiles showed statistical differences (Tukey s-b(K), p < 0.05). Re-rolling treatment significantly reduced the levels of alcoholic fatty acid-derived volatiles (FADVs) and volatile terpenoid (VTs), but increased the levels of aldehydic and ester FADVs, most amino acid-derived volatiles (AADVs), carotenoid-derived volatiles (CDVs), alkene VTs, and some other important volatile compounds. Based on the odor characteristics and fold changes of differential volatile compounds, hexanoic acid, hexyl formate, cis-3-hexenyl hexanoate, (Z)-3-hexenyl benzoate, hexyl hexanoate, phenylacetaldehyde, benzyl alcohol, β-ionone, α-ionone, dihydroactinidiolide, ipsenone, β-farnesene, β-octalactone, melonal, etc., were considered as the potential key odorants responsible for the floral and fruity scents of re-rolled black tea. In summary, this study provides a novel and simple processing technology to improve the aroma quality of small-leaf Congou black tea, and the results are beneficial to enriching tea aroma chemistry.

Milk Casein Inhibits Effect of Black Tea Galloylated Theaflavins to Inactivate SARS-CoV-2 In Vitro

Continuing caution is required against the potential emergence of SARS-CoV-2 novel mutants that could pose the next global health and socioeconomical threats. If virus in saliva can be inactivated by a beverage, such a beverage may be useful because the saliva of infected persons is the major origin of droplets and aerosols that mediate human-to-human viral transmission. We previously reported that SARS-CoV-2 was significantly inactivated by treatment in vitro with tea including green tea and black tea. Catechins and its derived compounds galloylated theaflavins (gTFs) bound to the receptor-binding domain (RBD) of the S-protein and blocked interaction between RBD and ACE2. Black tea is often consumed with sugar, milk, lemon juice, etc., and it remains unclarified whether these ingredients may influence the anti-SARS-CoV-2 effect of black tea. Here, we examined the effect of black tea on Omicron subvariants in the presence of these ingredients. The infectivity of Omicron subvariants was decreased to 1/100 or lower after treatment with black tea for 10 s. One or two teaspoons of milk (4~8 mL) completely blocked the anti-viral effect of a cup of tea (125 mL), whereas an addition of sugar or lemon juice failed to do so. The suppressive effect was dose-dependently exerted by milk casein but not whey proteins. gTFs were coprecipitated with casein after acidification of milk-supplemented black tea, strongly suggesting the binding of gTFs to casein. The present study demonstrates for the first time that an addition of milk cancelled the anti-SARS-CoV-2 effect of black tea due to binding of casein to gTFs.

Effects of Key Components on the Antioxidant Activity of Black Tea

Many components (such as tea polyphenols, catechins, theaflavins, theasinensins, thearubigins, flavonoids, gallic acid, etc.) in black tea have antioxidant activities. However, it is not clear which components have a greater influence on the antioxidant activity of black tea. In this study, the antioxidant activity and contents of tea polyphenols, catechins, theaflavins, thearubigins, theabrownins, TSA, total flavonoids, amino acids, caffeine, and total soluble sugar were analyzed in 51 black teas. Principal component analysis (PCA), orthogonal partial least-squares discrimination analysis (OPLS-DA), and the correlation analysis method were used for data analysis. The results showed that catechins in tea polyphenols were the most important components that determine the antioxidant activity of black tea. Among them, epicatechin gallate (ECG), epi-gallocatechin gallate (EGCG), epicatechin (EC), and epi-gallocatechin (EGC) were significantly positively correlated with the antioxidant activity of black tea, and theabrownin was negatively correlated with the antioxidant activity of black tea. Furthermore, this study analyzed the correlation between the changes in catechin and its oxidized polymers with antioxidant activity during black tea fermentation; it verified that catechins were significantly positively correlated with the antioxidant activity of black tea, and theabrownin showed a negative correlation. And the antioxidant activity of catechins and their oxidation products in vitro and their correlation in black tea processing were used as validation. This study provides a comparison method for comparing the antioxidant activity of black tea.

The adverse and beneficial effects of polyphenols in green and black teas in vitro and in vivo

Although numerous studies highlight the health benefits of tea, excessive consumption has been linked to toxic conditions. Thus, understanding the optimal consumption of tea is essential to minimize toxicity while maximizing its benefits. In this study, we investigated the effects of eight green tea samples (G1-G8) and eight black tea samples (R1-R8) from Camellia sinensis, the most popular teas in Asian culture, on RSC96 Schwann neural cells and embryonic cardiomyocyte H9c2 cells. The results showed that the IC50 (mg/ml, weight/volume) of both tea types were inversely proportional to their polyphenol content, suggesting a relationship between toxicity and polyphenol levels in both green and black tea. Interestingly, green teas generally have higher polyphenol content than black teas. We also assessed the protective effects of tea in vitro by pretreating cells with the teas at indicated doses of polyphenol and subsequently exposing them to H2O2. Both tea types significantly reduced the decline in cell viability for both cell lines, and there was no significant difference in protective polyphenol concentrations for green (G3 & G7) and black (R3 & R8) teas at effective concentrations (EC20 and EC40). To evaluate the preventative effects of tea in vivo, we examined the impact of two green (G3 & G7) and two black (R3 & R8) teas with varying polyphenol content on dextran sulfate sodium (DSS)-induced inflammatory colitis in mice. Tea-treated groups exhibited significantly lower inflammatory scores (DAI) than the control group. DSS treatment in the control group led to shortened colorectal lengths in mice, while tea co-treatment partially prevented this loss. Histological analysis revealed that G7 and R3 (with a moderate polyphenol content) treatment improved colorectal crypt structure, decreased the severity of inflammatory ulcerative colitis, and significantly reduced histological scores compared to the control group. However, G3 and R8 (with high and low doses of polyphenol content, respectively) did not show these effects, suggesting that a moderate polyphenol level in both tea types is optimal for preventative benefits.

Performance of Urinary Phenyl-γ-Valerolactones as Biomarkers of Dietary Flavan-3-ol Exposure

BACKGROUND

Phenyl-γ-valerolactones (PVLs) have been identified as biomarkers of dietary flavan-3-ol exposure, although their utility requires further characterization.

OBJECTIVES

We investigated the performance of a range of PVLs as biomarkers indicative of flavan-3-ol intake.

METHODS

We report the results of 2 companion studies: a 5-way randomized crossover trial (RCT) and an observational cross-sectional study. In the RCT (World Health Organization, Universal Trial Number: U1111-1236-7988), 16 healthy participants consumed flavan-3-ol-rich interventions (of apple, cocoa, black tea, green tea, or water [control]) for 1 d each. First morning void samples and 24-h urine samples were collected with diet standardized throughout. For each participant, 1 intervention period was extended (to 2 d) to monitor PVL kinetics after repeat exposure. In the cross-sectional study, 86 healthy participants collected 24-h urine samples, and concurrent weighed food diaries from which flavan-3-ol consumption was estimated using Phenol-Explorer. A panel of 10 urinary PVLs was quantified using liquid chromatography tandem mass spectrometry.

RESULTS

In both studies, 2 urinary PVLs [5-(3'-hydroxyphenyl)-γ-valerolactone-4'-sulfate and putatively identified 5-(4'-hydroxyphenyl)-γ-valerolactone-3'-glucuronide] were the principal compounds excreted (>75%). In the RCT, the sum of these PVLs was significantly higher than the water (control) after each intervention; individually, there was a shift from sulfation toward glucuronidation as the total excretion of PVLs increased across the different interventions. In the extended RCT intervention period, no accumulation of these PVLs was observed after consecutive days of treatment, and after withdrawal of treatment on the third day, there was a return toward negligible PVL excretion. All results were consistent, whether compounds were measured in 24-h urine or first morning void samples. In the observational study, the sum of the principal PVLs correlated dose dependently (Rs = 0.37; P = 0.0004) with dietary flavan-3-ol intake, with similar associations for each individually.

CONCLUSIONS

Urinary 5-(3'-hydroxyphenyl)-γ-valerolactone-4'-sulfate and putatively identified 5-(4'-hydroxyphenyl)-γ-valerolactone-3'-glucuronide are recommended biomarkers for dietary flavan-3-ol exposure.

Volatile, Microbial, and Sensory Profiles and Consumer Acceptance of Coffee Cascara Kombuchas

Given the substantial world coffee production, tons of coffee fruit cascara rich in bioactive compounds are discarded annually. Using this by-product to produce potentially healthy and acceptable foods is a sustainable practice that aggregates value to coffee production and may help improve people's lives. This study aimed to elaborate kombuchas from coffee cascara tea, evaluate their microbial profile, and monitor the changes in the volatile profile during fermentation, together with sensory attributes and acceptance by consumers from Rio de Janeiro (n = 113). Arabica coffee cascaras from Brazil and Nicaragua were used to make infusions, to which black tea kombucha, a Symbiotic Culture of Bacteria and Yeasts (SCOBY), and sucrose were added. Fermentation of plain black tea kombucha was also monitored for comparison. The volatile profile was analyzed after 0, 3, 6, and 9 days of fermentation via headspace solid phase microextraction GC-MS. A total of 81 compounds were identified considering all beverages, 59 in coffee cascara kombuchas and 59 in the black tea kombucha, with 37 common compounds for both. An increase mainly in acids and esters occurred during fermentation. Despite the similarity to black tea kombucha, some aldehydes, esters, alcohols, and ketones in coffee cascara kombucha were not identified in black tea kombucha. Potential impact compounds in CC were linalool, decanal, nonanal, octanal, dodecanal, ethanol, 2-ethylhexanol, ethyl acetate, ethyl butyrate, ethyl acetate, β-damascenone, γ-nonalactone, linalool oxide, phenylethyl alcohol, geranyl acetone, phenylacetaldehyde, isoamyl alcohol, acetic acid, octanoic acid, isovaleric acid, ethyl isobutyrate, ethyl hexanoate, and limonene. The mean acceptance scores for cascara kombuchas varied between 5.7 ± 0.53 and 7.4 ± 0.53 on a nine-point hedonic scale, with coffee cascara from three-day Nicaragua kombucha showing the highest score, associated with sweetness and berry, honey, woody, and herbal aromas and flavors. The present results indicate that coffee cascara is a promising by-product for elaboration of fermented beverages, exhibiting exotic and singular fingerprinting that can be explored for applications in the food industry.

New Hydrolyzable Tannin with Potent Antioxidant and α-Glucosidase Inhibitory Activity from Black Tea Produced from Camellia taliensis

Camellia taliensis (W. W. Smith) Melchior, belonging to the genus Camellia sect. Thea., is mainly distributed from northern Myanmar to western and southwestern Yunnan province of China, and its leaves have been used to make various teas by the locals of its growing regions. The chemical constituents of C. taliensis are significantly related to those of cultivated tea plants, C. sinensis and C. sinensis var. assamica. The HPLC-ESI-MS analysis of black tea prepared from the leaves of C. taliensis showed a rich existence of polyphenols. Further comprehensive chemical study led to the separation and recognition of 32 compounds (1-32), including one new hydrolyzable tannin, 1-O-galloyl-4,6-tetrahydroxydibenzofurandicarboxyl-β-D-glucopyranose (1), and one new natural product (24). The known compounds referred to seven hydrolyzable tannins (2-8), 10 flavonols and glycosides (9-18), and 14 simple phenolics (19-32). Their structures were elucidated by comprehensive spectroscopic analyses. Among them, 20 compounds (2, 3, 6, 7, 8, 15, 17, 18, 20-22, 24-32) were isolated from black tea for the first time. Most isolates displayed obvious antioxidant activities on DPPH and ABTS⁺ assays, and the hydrolyzable tannins 1, 3-5, 7, and 8 exhibited stronger inhibitory activities on α-glycosidase than quercetin and acarbose (IC₅₀ = 5.75 and 223.30 μM, respectively), with IC₅₀ values ranging from 0.67 to 2.01 μM.

Effects of Sun Withering Degree on Black Tea Quality Revealed via Non-Targeted Metabolomics

In this study, the effects of different sun withering degrees (75% (CK), 69% (S69), 66% (S66), 63% (S63), and 60% (S60) water content in the withered leaves) on black tea sensory quality were investigated by means of sensory evaluation plus metabolomics analysis. Sensory evaluation results showed higher sensory quality scores for the black tea in S69-S66, due to better freshness, sweeter taste, and a sweet and even floral and fruity aroma. Additionally, 65 non-volatile components were identified using Ultra Performance Liquid Chromatography-Quadrupole-Time of Flight-Mass Spectrometry (UPLC-Q-TOF/MS). Among them, the content increase of amino acids and theaflavins was found to promote the freshness and sweetness of black tea. The aroma of tea was analyzed using combined Solvent Assisted Flavor Evaporation-Gas Chromatography-Mass Spectrometry (SAFE-GC-MS) and Headspace-Solid Phase Micro Extract-Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS), and 180 volatiles were identified, including 38 variable importance in projection (VIP) > 1 (p < 0.05) and 25 Odor Activity Value (OAV) > 1 volatiles. Statistical analysis revealed 11 volatiles as potential major aroma differential metabolites in black tea with a different sun withering degree, such as volatile terpenoids (linalool, geraniol, (E)-citral, and β-myrcene), amino-acid-derived volatiles (benzeneethanol, benzeneacetaldehyde, and methyl salicylate), carotenoid-derived volatiles (jasmone and β-damascenone), and fatty-acid-derived volatiles ((Z)-3-hexen-1-ol and (E)-2-hexenal). Among them, volatile terpenoids and amino acid derived volatiles mainly contributed to the floral and fruity aroma quality of sun-withered black tea.

Black tea bioactive phytoconstituents realign NRF2 for anticancer activity in lung adenocarcinoma

Constitutive activation of nuclear factor erythroid 2-related factor 2 (NRF2) is pivotal in bestowing therapy resistance in cancer cells. Several phytochemicals have been reported with the potential of modulating NRF2. Therefore, it was hypothesized that NRF2-deregulated chemoresistance in lung adenocarcinoma (LUAD) may be counteracted by theaflavin-rich black tea (BT). A non-responsive LUAD cell line, A549, was the best sensitized towards cisplatin upon pre-treatment with BT. BT-mediated NRF2 reorientation was observed to be dependent on concentration and duration of treatment as well as on the mutational profile of NRF2 in A549 cells. Transient exposure of low-concentration BT hormetically downregulated NRF2, its downstream antioxidants, and drug transporter. BT also influenced the Kelch-like ECH-associated protein (KEAP1)-dependent cullin 3 (Cul3) and KEAP-1-independent signaling through epidermal growth factor receptor (EGFR) - rat sarcoma virus (RAS) - rapidly accelerated fibrosarcoma (RAF) - extracellular signal-regulated kinase 1/2 (ERK) - matrix metalloproteinase (MMP)-2 and MMP-9. The realignment of NRF2 in KEAP1-suppressed A549 cells enhanced the chemotherapeutic outcome. But a higher concentration of the same BT surprisingly upregulated NRF2 and its transcriptional targets with a subsequent decrease in the NRF2-regulatory machinery in NCI-H23 cells (a KEAP1-overexpressed LUAD cell line), ultimately resulting in a better anticancer response. The BT-mediated bidirectional NRF2 modulation was reconfirmed upon comparison with the action of a pharmacological NRF2 inhibitor, ML-385, in A549 and a known NRF2 activator, tertiary-butylhydroquinone, in NCI-H23 respectively. BT-mediated regulation of NRF2-KEAP1 and their upstream networks (EGFR/RAS/RAF/ERK) sufficed as a better anticancer agent than synthetic NRF2 modulators. Therefore, BT may be indicated as a potent multi-modal small molecule for increasing drug responsiveness in LUAD cells by maintaining NRF2/KEAP1 axis at an optimum level.

Impact of Grape Seed Powder and Black Tea Brew on Lipid Digestion-An In Vitro Co-Digestion Study with Real Foods

Effects of two foods with bioactive constituents (black tea brew, BTB and grape seed powder, GSP) on lipid digestibility was studied. Lipolysis inhibitory effect of these foods was examined using two test foods (cream and baked beef) with highly different fatty acid (FA) composition. Digestion simulations were performed either using both gastric and pancreatic lipase, or only with pancreatic lipase according to the Infogest protocol. Lipid digestibility was assessed based on the bioaccessible FAs. Results showed the triacylglycerols containing short- and medium-chain FAs (SCFA and MCFA) are non-preferred substrates for pancreatic lipase; however, this is not characteristic for GL. Our findings suggest that both GSP and BTB primarily affect the lipolysis of SCFAs and MCFAs, because the dispreference of pancreatic lipase towards these substrates was further enhanced as a result of co-digestion. Interestingly, GSP and BTB similarly resulted in significant decrease in lipolysis for cream (containing milk fat having a diverse FA profile), whereas they were ineffective in influencing the digestion of beef fat, having simpler FA profile. It highlights that the characteristics of the dietary fat source of a meal can be a key determinant on the observed extent of lipolysis when co-digested with foods with bioactive constituents.

Uniaxial Rotational Molding of Bio-Based Low-Density Polyethylene Filled with Black Tea Waste

In this paper, the possibility of obtaining uniaxially rotomolded composite parts was discussed. The used matrix was bio-based low-density polyethylene (bioLDPE) filled with black tea waste (BTW) to prevent the thermooxidation of samples during processing. In rotational molding technology, the material is held at an elevated temperature in a molten state for a relatively long time, which can result in polymer oxidation. The Fourier transform infrared spectroscopy (FTIR) shows that adding 10 wt% of black tea waste has not led to the formation of carbonyl compounds in polyethylene, and adding 5 wt% and above prevents the appearance of the C-O stretching band connected with degradation of LDPE. The rheological analysis proved the stabilizing effect of black tea waste on the polyethylene matrix. The same temperature conditions of rotational molding did not change the chemical composition of black tea but slightly influenced the antioxidant activity of methanolic extracts; the detected changes suggest degradation is a color change, and the total color change parameter (ΔE) is 25. The oxidation level of unstabilized polyethylene measured using the carbonyl index exceeds 1.5 and gradually decreases with the addition of BTW. The BTW filler did not influence the melting properties of bioLDPE; the melting and crystallization temperature remained stable. The addition of BTW deteriorates the composite mechanical performance, including Young modulus and tensile strength, compared to the neat bioLDPE.

Study on the Trend in Microbial Changes during the Fermentation of Black Tea and Its Effect on the Quality

The role of tea endophytes in black tea fermentation and their impact on black tea quality remain unclear. We collected fresh leaves of Bixiangzao and Mingfeng tea and processed them into black tea, while testing the biochemical composition of both the fresh leaves and the black tea. We also used high-throughput techniques, such as 16S rRNA, to analyze the dynamic changes in the microbial community structure and function during black tea processing in order to investigate the influence of dominant microorganisms on the quality of black tea formation. Our results showed that bacteria, such as Chryseobacterium and Sphingomonas, and Pleosporales fungi dominated the entire black tea fermentation process. Predicted functional analysis of the bacterial community indicated that glycolysis-related enzymes, pyruvate dehydrogenase, and tricarboxylic acid cycle-related enzymes were significantly elevated during the fermentation stage. Amino acids, soluble sugars, and tea pigment content also increased considerably during fermentation. Pearson's correlation analysis revealed that the relative bacterial abundance was closely related to the content of tea polyphenols and catechins. This study provides new insights into the changes in microbial communities during the fermentation of black tea and demonstrates understanding of the basic functional microorganisms involved in black tea processing.

Supplementation with a New Standardized Extract of Green and Black Tea Exerts Antiadipogenic Effects and Prevents Insulin Resistance in Mice with Metabolic Syndrome

Insulin resistance is one of the main characteristics of metabolic syndrome (MetS) and the main cause of the development of type II diabetes. The high prevalence of this syndrome in recent decades has made it necessary to search for preventive and therapeutic agents, ideally of natural origin, with fewer side effects than conventional pharmacological treatments. Tea is widely known for its medicinal properties, including beneficial effects on weight management and insulin resistance. The aim of this study was to analyze whether a standardized extract of green and black tea (ADM^® Complex Tea Extract (CTE)) prevents the development of insulin resistance in mice with MetS. For this purpose, C57BL6/J mice were fed for 20 weeks with a standard diet (Chow), a diet with 56% kcal from fat and sugar (HFHS) or an HFHS diet supplemented with 1.6% CTE. CTE supplementation reduced body weight gain, adiposity and circulating leptin levels. Likewise, CTE also exerted lipolytic and antiadipogenic effects in 3T3-L1 adipocyte cultures and in the C. elegans model. Regarding insulin resistance, CTE supplementation significantly increased plasma adiponectin concentrations and reduced the circulating levels of insulin and the HOMA-IR. Incubation of liver, gastrocnemius muscle and retroperitoneal adipose tissue explants with insulin increased the pAkt/Akt ratio in mice fed with Chow and HFHS + CTE but not in those fed only with HFHS. The greater activation of the PI3K/Akt pathway in response to insulin in mice supplemented with CTE was associated with a decrease in the expression of the proinflammatory markers Mcp-1, IL-6, IL-1β or Tnf-α and with an overexpression of the antioxidant enzymes Sod-1, Gpx-3, Ho-1 and Gsr in these tissues. Moreover, in skeletal muscle, mice treated with CTE showed increased mRNA levels of the aryl hydrocarbon receptor (Ahr), Arnt and Nrf2, suggesting that the CTE's insulin-sensitizing effects could be the result of the activation of this pathway. In conclusion, supplementation with the standardized extract of green and black tea CTE reduces body weight gain, exerts lipolytic and antiadipogenic effects and reduces insulin resistance in mice with MetS through its anti-inflammatory and antioxidant effects.

Anticariogenic Activity of Black Tea: An In Vivo Study

BACKGROUND

The prevention of dental caries has always remained a challenge. Caries prevention through dietary intervention holds promise. Studies have revealed that several constituents present in tea have anticariogenic properties. Tea is a widely consumed beverage and hence could be utilized as a suitable caries preventive agent. The purpose of this study was to determine the effect of black tea on caries progression in experimental animals.

MATERIALS AND METHODS

This study was carried out in 17-day-old albino rat pups. The animals were divided into three groups, with eight animals in each group. They were fed on a cariogenic diet (MIT 200) and inoculated with Streptococcus mutans. Group I was given MIT 200 with water, Group II was placed on MIT 200 with black tea, and Group III was placed on MIT 200 with fluoridated water for a period of 45 days. After 45 days, the animals were killed under ether anesthesia, and their teeth were examined for caries.

RESULTS

The carious lesions were scored for the first two molars in each quadrant. In each group, a total of 64 teeth were examined. The caries score between the upper and lower jaws was compared using ANOVA.

CONCLUSION

From this study, it may be inferred that drinking black tea reduced the development of dental caries in young rats fed on a cariogenic diet. The tea used for this study was prepared using fluoride-free water, so we can assume that besides fluoride, certain components are present in tea leaves that possess anticariogenic properties.

Theaflavins in Black Tea Mitigate Aging-Associated Cognitive Dysfunction via the Microbiota-Gut-Brain Axis

Aging-associated cognitive dysfunction has a great influence on the lifespan and healthspan of the elderly. Theaflavins (TFs), a mixture of ingredients formed from enzymatic oxidation of catechins during the manufacture of tea, have a positive contribution to the qualities and antiaging activities of black tea. However, the role of TFs in mitigating aging-induced cognitive dysfunction and the underlying mechanism remains largely unknown. Here, we find that TFs effectively improve behavioral impairment via the microbiota-gut-brain axis: TFs maintain gut homeostasis by improving antioxidant ability, strengthening the immune response, increasing the expression of tight junction proteins, restructuring the gut microbiota, and altering core microbiota metabolites, i.e., short-chain fatty acids and essential amino acids (SCFAs and AAs), and upregulating brain neurotrophic factors. Removing the gut microbiota with antibiotics partly abolishes the neuroprotective effects of TFs. Besides, correlation analysis indicates that the decrease in gut microbiota, such as Bacteroidetes and Lachnospiraceae, and the increase in microbiota metabolites' levels are positively correlated with behavioral improvements. Taken together, our findings reveal a potential role of TFs in mitigating aging-driven cognitive dysfunction via the microbiota-gut-brain axis. The intake of TFs can be translated into a novel dietary intervention approach against aging-induced cognitive decline.

In silico molecular modeling and simulations of black tea theaflavins revealed theaflavin-3'-gallate as putative liver X receptor-beta agonist

The low constitutive activation of Liver X receptor, an endogenous nuclear receptor with two subtypes (α and β), is a condition lying at the crossroad of cancer and cardiovascular disease. Both natural and synthetic Liver X receptor agonists have reportedly shown remarkable antiproliferative and atheroprotective effects but the repeated doses of its synthetic ones are also paradoxically associated with hyperlipidaemic effects and neurotoxicity, though attributed to the alpha subtype. This highlights the need for novel, safe, and potent LXR-beta-selective agonists. Hypocholesterolaemic effects of black theaflavins have been widely reported, but data on the exact theaflavin compound (s) responsible for these effects is currently lacking. Neither is information on the possible modulatory effects of the compound (s) on LXR-beta nor its possible implications in the context of drug development for cardiovascular diseases and cancers is explored. On this account, we investigated the potential interaction of four main theaflavin monomers (TF1, TF2A, TF2B & TF3) with human LXR-beta through robust computational modelling that entails molecular docking, free energy calculations and molecular dynamics simulations. The ligands were further profiled (in silico) for absorption, distribution, metabolism, excretion, and toxicological properties. Our result revealed theaflavin TF2B as a putative LXR-beta agonist, possibly responsible for the widely observed hypocholesterolaemic effect in black tea. This finding, while encouraging, needs to be experimentally verified in wet studies.Communicated by Ramaswamy H. Sarma.

Association between Different Types of Tea Consumption and Risk of Gynecologic Cancer: A Meta-Analysis of Cohort Studies

Plenty of studies have shown that tea has an effect of inhibiting gynecologic tumors. However, there still remained controversy of the association between tea and gynecologic tumors in epidemiological studies. In this study, PubMed, Embase, and Cochrane Database were used to search the literature from 1 January 1960 to 26 December 2022 to investigate the association between tea intake and gynecologic cancer risk. In total, 19 cohort studies with 2,020,980 subjects and 12,155 gynecological tumor cases were retrieved. The pooled relative risk (RR) of gynecologic tumor for tea intake was 1.00 (95% CI: 0.96-1.04). RRs were 0.94 (95% CI: 0.88-1.01) for ovarian cancer, 1.02 (95% CI: 0.97-1.07) for endometrial cancer, and 1.06 (95% CI: 0.91-1.23) for cervical cancer. Subgroup analyses were adopted based on the tea type and geographic location. Interestingly, significant preventive impact of non-herbal tea on ovarian cancer (pooled relative risk: 0.67; 95% CI: 0.55-0.81) was found, especially for black tea (pooled relative risk: 0.64; 95% CI: 0.51-0.80). Dose-response analysis indicated that although it is not statistically significant, a decreasing trend of ovarian cancer risk could be observed when the tea consumption was 1.40 to 3.12 cups/day. In conclusion, our findings suggested that ovarian cancer, but not other gynecologic cancers, could possibly be prevented by drinking non-herbal tea. In addition, the preventive impact of green tea on gynecologic cancer seemed to be relatively weak and needs further cohorts to validate it.

The Effects of Black Tea Consumption on Intestinal Microflora-A Randomized Single-Blind Parallel-Group, Placebo-Controlled Study

We previously reported that black tea consumption for 12 wk reduced the risk of acute upper respiratory tract inflammation, and improved secretory capacity in individuals with low salivary SIgA levels (Tanaka Y et al. 2021. Jpn Pharmacol Ther 49: 273-288). These results suggested that habitual black tea consumption improves mucosal immunity. Therefore, in this study we evaluated the effect of black tea intake on gut microbiota, which is known to be involved in mucosal immunity, by analyzing the bacterial flora and the short-chain fatty acids (SCFAs) concentration of feces collected during the above clinical study. The clinical design was a randomized, single-blind, parallel-group, placebo-controlled study with 72 healthy Japanese adult males and females, who consumed three cups of black tea (Black Tea Polymerized Polyphenols 76.2 mg per day) or placebo per day for 12 wk. In all subjects intake of black tea significantly increased abundance of Prevotella and decreased fecal acetic acid concentration. Particularly in the subjects with low salivary SIgA levels, the change over time of total bacteria, Prevotella, and butyrate-producing bacteria, which are involved in normalizing immune function, were higher in the black tea group than in the placebo group. In subjects with low abundance of Flavonifractor plautii a butyrate-producing bacteria, black tea consumption significantly increased salivary SIgA concentration and the absolute number of Flavonifractor plautii. In conclusion, our results suggest that improvement of mucosal immunity via an increase in butyrate-producing bacteria in the gut may partly contribute to the suppressive effect of black tea consumption on acute upper respiratory tract inflammation observed in our previous report.

GC-MS and LC-MS Pesticide Analysis of Black Teas Originating from Sri Lanka, Iran, Turkey, and India

The purpose of this study is to investigate pesticide residues in the imported and domestic tea sold in Turkey and to detect their compliance with maximum residue limits (MRL) and Acceptable Daily Intake (ADI). A total of 79 samples were analyzed by using LC-MS/MS and GC-MS devices with AOAC 2007.01 method to investigate 603 pesticide residues. According to the results, pesticide residues were found in a total of 28 tea samples. Pesticide residues were found in the countries of origin at the rates as follows: Iran (100%), India (33.3%) and Sri Lanka (17.3%). No pesticide residue was detected in the tea produced in Turkey. The compounds such as Diuron, Ethion, Cypermethrin, Thiacloprid, Thiamethoxam, Fenpyroximate, Acetamiprid, Imidacloprid, Flubendiamide, Deltamethrin and Hexythiazox were detected in positive samples. Seven types of pesticide residues exceeded the MRL determined by the Turkish Food Codex for 15 types (53.57%) for 28 samples with pesticide residue detected. Additionally, 4 types of pesticide residues were determined to exceed the ADI determined by the Codex Alimentarius for 13 (46.42%) of 28 samples with pesticide residue detected. These results have showed that the imported tea entering Turkey was not adequately analyzed in the customs control laboratories or the maximum residual limits were not clearly determined.

Preventive Effects of Different Black and Dark Teas on Obesity and Non-Alcoholic Fatty Liver Disease and Modulate Gut Microbiota in High-Fat Diet Fed Mice

Non-alcoholic fatty liver disease (NAFLD) has emerged as a leading public health challenge and is closely associated with metabolic syndromes, such as obesity. Intestinal microbiota dysbiosis could play a vital role in the pathogenesis and progression of NAFLD. Tea is the second most popular health drink in the world behind water, and exhibits many health-promoting effects. In this study, the protective effects of different black and dark teas on NAFLD induced by long-term high-fat diet (HFD) exposure and their regulation of gut microbiota were evaluated and explored. The results indicated that supplementation with different black and dark tea extracts could significantly suppress the energy intake, alleviate abnormal accumulation of visceral fat, and prevent obesity, hepatic abnormal lipid deposition and liver steatosis in HFD-fed mice at varying degrees. In addition, Dianhong tea and Liupao tea interventions could significantly decrease the ratio of Firmicutes to Bacteroidetes, and selenium-enriched black tea and selenium-enriched dark rea supplementation could remarkably reduce the relative abundance of Actinobacteria compared to the model group. Moreover, these teas could partly shift the relative abundances of Allobaculum, Roseburia and Dubosiella. Taken together, black teas and dark teas could prevent HFD-induced features of obesity and NAFLD, which might partly be due to the modulation of gut microbiota.

Nano-visualization of the in vitro antiviral activity of black tea based on production area using a liposome-based virus membrane model

Black tea extracts (BTEs) from four different production areas showed a higher aggregation strength for phosphatidylcholine-based liposomes containing cholesterol used as a viral membrane model. Furthermore, the anti-influenza A virus (IAV) activity of each BTE in vitro demonstrated that although Sri Lanka, Kenya, and Assam had higher anti-IAV activities, Darjeeling had a lower anti-IAV activity, showing a correlation between each BTE and the liposome aggregation strength. Moreover, the antiviral activity strength of BTEs was consistent with the antioxidant activity strength of BTEs, suggesting that the component(s) in black tea that exhibits antioxidant activity would also be the component(s) that accounts for its antiviral activity. Thus, our results propose that BTEs exert their antiviral effects by binding not only hemagglutinin and neuraminidase but also viral membranes directly, especially "cholesterol-rich lipid rafts" and affects the membrane structure, causing the virus to aggregate, thereby inhibiting infection of the host cells.

Effects of Multiscale Mechanical Pulverization on the Physicochemical and Functional Properties of Black Tea

Black tea leaves were pulverized at an organ-scale (~mm), tissue-scale (500−100 μm) and cell-scale (<50−10 μm) to investigate their physicochemical and functional properties. The results showed that cell-scale powders exhibited a bright brown color compared with organ- or tissue-scale powders with the highest total color difference (∆E) of 39.63 and an L value of 55.78. There was no obvious difference in the oil-holding capacity (OHC) of the organ- and tissue-scale powders (3.71−3.74 g/g), while the OHC increased significantly to 4.08 g/g in cell-scale powders. The soluble dietary fiber (SDF) content of cell-scale powders increased remarkably to 10.41%, indicating a potential application as a high-SDF food. Further, cell-scale pulverization of black tea enhanced its DPPH scavenging activity and ferric-ion-reducing antioxidant power (FRAP). However, the polyphenol content (13.18−13.88%) and the protein content (27.63−28.09%), as well as the Pb2+ adsorption capacity (1.97−1.99 mg/g) were not affected by multiscale pulverizations. The mean particle size (D50) correlated linearly with tap density (TD), color parameters of L and b, SDF content, DPPH scavenging activity and FRAP. The results indicate that black tea powders pulverized at a cell-scale can be used as a soluble fiber-rich functional food additive with a bright color, enhanced OHC and antioxidant capacity.

Investigating particle-size-induced changes in composition, physical, rheological, and bioactive properties of black tea powder

BACKGROUND

People brew tea to drink an infusion that only contains 25% water-soluble constituents, leading to most of the insoluble materials being wasted. Tea powder could be drunk directly by mixing with water without producing any waste. Tea powder can also be used as a natural additive to improve the flavour and taste in beverages and foods. Much detailed information on the particle properties of tea powder is required with its increasing consumption. The aim of this study was to investigate the effects of particle size ranging from median diameter D₅₀  = 4.32 to 26.59 μm on the composition, physical, rheological, and bioactive properties of black tea powder.

RESULTS

The results indicate that large powder sizes had high bulk density and flowability, whereas small powder sizes possessed good swelling ability and wettability. The contents of water extract, total polyphenols, crude fibre, catechins, and thearubigins reduced with a decrease in particle size. To change the particle size and concentration could adjust the elastic modulus and the viscous modulus of the black tea powder suspension. Moreover, black tea powder with small particle size could regulate blood lipids in a hyperlipidaemic rat model by lowering triacylglycerols and elevating high-density lipoprotein cholesterol, whereas large particles presented an advantage in reducing body weight.

CONCLUSION

Our investigation extended the knowledge of commercial black tea powder in composition, physical, rheological, and bioactive properties. These results lay the foundation for future exploration of the use of tea powder in the food industry. © 2022 Society of Chemical Industry.

Identification and characterization of the key volatile flavor compounds in black teas from distinct regions worldwide

Volatile flavor compounds in 112 black teas from seven countries were analyzed by untargeted metabolomics using headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME/GC-MS). Multivariate statistical analysis and odor activity values (OAVs) were used to classify these samples and identify key odorants. A total of 140 volatile flavor compounds (VFCs), including 12 different groups, were identified, and alcohols were prevalent in China and India samples, accounting for 40.83% and 34.96% of the total VFCs, respectively. Eight volatile compounds with OAVs > 1 were identified as key active differential odorants in Chinese, Indian, and Sri Lankan samples, including linalool, pentanoic acid, methyl salicylate, hexanoic acid, 1-methyl-naphthalene, phenylethyl alcohol, geraniol, and β-ionone. Linalool, pentanoic acid, and hexanoic acid in Indian black teas, phenylethyl alcohol in Chinese black teas, and 1-methyl-naphthalene, β-ionone in Sri Lankan black teas could be used to discriminate different black tea groups. A total of 12-14 VFCs with OAVs > 1 were identified as key active aromatics in Chinese black tea sample. Linalool and benzeneacetaldehyde in Yingde (Guangdong) black tea, methyl salicylate in Taiwanese samples, and benzeneacetic acid in Anhui black tea could be used as biomarkers to distinguish them from other Chinese samples. Sensory evaluation results showed that most black teas presented the common sweet, floral odors, which were consistent with GC-MS analysis. These results will contribute to characterize the odor metabolome of black teas and provide biochemical basis for identifying the authenticity of different black teas. PRACTICAL APPLICATION: Linalool, pentanoic acid, and hexanoic acid in Indian black teas, phenylethyl alcohol in Chinese black teas, 1-methyl-naphthalene, β-ionone, and methyl salicylate in Sri Lankan black teas could be used to discriminate black teas from the three countries. Linalool and benzeneacetaldehyde in Yingde black teas, methyl salicylate in Taiwanese black teas, and benzeneacetic acid in Anhui black tea are the potential biomarkers to distinguish these teas from other Chinese black teas.

Effect of Strobilanthes tonkinensis Lindau Addition on Black Tea Flavor Quality and Volatile Metabolite Content

The characteristic aroma of Chinese black tea (BT) produced in summer usually lacks intensity and persistence, reducing consumer acceptance and market demand. Strobilanthes tonkinensis Lindau (STL) possesses excellent biological characteristics, making it a promising novel tea ingredient. We investigated the effects of different addition methods and concentrations for the novel additive STL on the sensory quality of BT. A 20:1500 g/g addition to rolled tea leaves was identified as the best BT with STL (BoS) treatment. We identified 141 volatile metabolites (VMs) for the first time in STL, with high alcohol, ester, ketone, enyne, alkyne, and alkane contents. Partial least-squares discriminant analysis distinguished the samples and revealed 28, 26, and 14 differential VMs in STL vs. BoS, BT vs. STL, and BT vs. BoS comparisons, respectively. Using a combination of Venn, multiple experiment viewer, and odor activity value analysis, 16 key differential VMs were identified. Compared to BT, the 1-octen-3-ol, 1-hexanol, 1-dodecanol, (E)-3-hexen-1-ol, phenylethyl alcohol, and 2-methoxy-3-(2-methylpropyl)-pyrazine contents in BoS were 394.7%, 53.6%, 34.1%, 24.4%, 9.9%, and 5.7% higher, respectively. BoS combined the aromatic properties of BT and STL into a sweet and glutinous rice flavor. The results provide theoretical support for future research and development of novel BT-based products.

New insights into the effect of fermentation temperature and duration on catechins conversion and formation of tea pigments and theasinensins in black tea

BACKGROUND

The phenol oxidative pathway during fermentation remains unclear. To elucidate the effect of fermentation on phenol conversion, we investigated the effects of fermentation temperature and duration on the conversion of catechins and the formation of theasinensins (TSs), theaflavins (TFs), thearubigins (TRs), and theabrownins (TBs).

RESULTS

During fermentation, TSs formation increased initially and then decreased. Long fermentation durations were unfavorable for liquor brightness (LB) and resulted in the production of large amounts of TRs and TBs. Low fermentation temperatures (20 °C and 25 °C) favored the maintenance of polyphenol oxidase activity and the continuous formation of TFs, TSs, and TRSI (a TRs fraction), resulting in better LB and liquor color. Higher temperatures (30 °C, 35 °C, and 40 °C) resulted in higher peroxidase activity, higher oxidative depletion rates of catechins, and excessive production of TRSII (a TRs fraction) and TBs. Analysis of the conversion pathway of polyphenolic compounds during fermentation showed that, during early fermentation, large amounts of catechins were oxidized and converted to TFs and theasinensin B. As fermentation progressed, considerable amounts of theaflavin-3'-gallate, theasinensin A, theaflavin-3-gallate, theaflavin-3,3'-digallate, and theasinensin C were produced and then converted to TRSI; in the final stage, TRSII and TBs were converted continuously.

CONCLUSION

Different fermentation temperature and duration combinations directly affected the type and composition of phenolic compounds. The key conditions for controlling phenolic compound conversion and fermentation direction were 60 or 90 min and 25 or 30 °C. Our study provides insights into the regulation of phenolic compound conversion during black tea fermentation. © 2021 Society of Chemical Industry.

Changes of some bioactive and physicochemical properties during the black tea processing

In this research, some physical and bioactive properties of tea samples collected from every processing stage of black tea production were investigated. The processing stages were significantly effective on the investigated properties (moisture content, color parameters [L^* , a^* , and b^* ], and pH values the total phenolic substance, antioxidant activity) (p < 0.01). The antioxidant activities were found to be at a high level in fresh tea but decreased during the processing stages. Furthermore, the lowest activity was observed in the drying stage for extracts prepared with water and in the drying and sorting stages for extracts prepared with ethanol. In addition, it was determined that palmitic acid, myristic acid, and capric acid as saturated fatty acids, oleic acid, heptadecenoic acid, and eicosenoic acid as unsaturated fatty acids formed the fatty acid profile. Palmitic acid was determined to be the dominant fatty acid in tea samples. PRACTICAL APPLICATION: Tea is a beverage known to have positive health effects. The chemical structure of tea is very effective in providing these positive effects on health. Black tea production takes place in five stages in general terms (withering, rolling, oxidation, drying, and sorting stages) after the harvesting. These processes are very effective in the quality properties of tea. This research provides information about effects of processing stages on black tea. Our results demonstrate that processing was significantly effective on the physicochemical and bioactive properties of tea. Functionality of bioactive compounds could be maintained by optimization of the applied processes.

Mycotoxins along the tea supply chain: A dark side of an ancient and high valued aromatic beverage

ABSTRACTSTea (Camellia sinensis L.) is a high valued beverage worldwide since ancient times; more than three billion cups of tea are consumed each day. Leaf extracts of the plant are used for food preservation, cosmetics, and medicinal purposes. Nevertheless, tea contaminated with mycotoxins poses a serious health threat to humans. Mycotoxin production by tea fungi is induced by a variety of factors, including poor processing methods and environmental factors such as high temperature and humidity. This review summarizes the studies published to date on mycotoxin prevalence, toxicity, the effects of climate change on mycotoxin production, and the methods used to detect and decontaminate tea mycotoxins. While many investigations in this domain have been carried out on the prevalence of aflatoxins and ochratoxins in black, green, pu-erh, and herbal teas, much less information is available on zearalenone, fumonisins, and Alternaria toxins. Mycotoxins in teas were detected using several methods; the most commonly used being the High-Performance Liquid Chromatography (HPLC) with fluorescence detection, followed by HPLC with tandem mass spectrometry, gas chromatography and enzyme-linked immunosorbent assay. Further, mycotoxins decontamination methods for teas included physical, chemical, and biological methods, with physical methods being most prevalent. Finally, research gaps and future directions have also been discussed.

Black Tea Reduces Diet-Induced Obesity in Mice via Modulation of Gut Microbiota and Gene Expression in Host Tissues

Black tea was reported to alter the microbiome populations and metabolites in diet-induced obese mice and displays properties that prevent obesity, but the underlying mechanism of the preventative effect of black tea on high-fat diet (HFD) induced obesity has not been elucidated. Epigenetic studies are a useful tool for determining the relationship between obesity and environment. Here, we show that the water extract of black tea (Lapsang souchong, LS) reverses HFD-induced gut dysbiosis, alters the tissue gene expression, changes the level of a major epigenetic modification (DNA methylation), and prevents obesity in HFD feeding mice. The anti-obesity properties of black tea are due to alkaloids, which are the principal active components. Our data indicate that the anti-obesity benefits of black tea are transmitted via fecal transplantation, and the change of tissue gene expression and the preventative effects on HFD-induced obesity in mice of black tea are dependent on the gut microbiota. We further show that black tea could regulate the DNA methylation of imprinted genes in the spermatozoa of high-fat diet mice. Our results show a mechanistic link between black tea, changes in the gut microbiota, epigenetic processes, and tissue gene expression in the modulation of diet-induced metabolic dysfunction.

Effects of black tea and black brick tea with fungal growth on lowering uric acid levels in hyperuricemic mice

Black tea, a traditional drink, can induce urination and quench thirst. Black brick tea with fungal growth, prepared by steaming, pressing, inducing fungal growth, and drying the black tea, is a new type of black tea with different sensory qualities and is suitable for storage. However, the effects of black brick tea with fungal growth on lowering uric acid are still unexplored. Therefore, the potassium oxonate was administered for 7 consecutive days to establish the hyperuricemic mice. Then allopurinol, black tea, and black brick tea with fungal growth were orally administered with hyperuricemic mice for 14 days. Serum uric acid levels, liver xanthine oxidase (XOD) and adenosine deaminase (ADA) activities, and expression of renal urate transporters and inflammatory response were detected. Compared to the model group, both types of black tea lowered serum uric acid by decreasing the uric acid production with inhibiting the activities of XOD and ADA, and increasing uric acid excretion because of downregulating urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) expressions, and upregulating organic anion transporter 1 (OAT1), organic anion transporter 3 (OAT3), and organic cation transporter 1 (OCT1) expressions. They could also improve renal injury by suppressing the activation of the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome, and nuclear factor-κB (NF-κB) signaling, thereby reducing renal proinflammatory cytokine levels. Compared with black tea, black brick tea with fungal growth with a higher content of theabrownins had a better effect on lowering serum uric acid. PRACTICAL APPLICATIONS: Black tea accounts for approximately 78% of the total consumed tea in the world. Black brick tea with fungal growth is a new kind of black tea product with different sensory qualities and is suitable for storage. The study found that black brick tea with fungal growth is superior to black tea in reducing serum uric acid levels, which make a significant contribution to promote people's health and stimulate the production and consumption of black brick tea with fungal growth. In addition, it provides a clue for future research to identify the effective components of black brick tea with fungal growth lowering uric acid.

Characterization of the Key Aroma Compounds of Three Kinds of Chinese Representative Black Tea and Elucidation of the Perceptual Interactions of Methyl Salicylate and Floral Odorants

Jinjunmei (JJM), Keemun (KM), and Dianhong (DH) are the representative black teas in China, and they have always been favored by consumers. In this study, we aim to obtain the aroma characteristic information of volatile components in black tea samples through headspace solid-phase microextraction (HS-SPME), solvent-assisted flavor evaporation (SAFE), and gas chromatography-mass spectrometry combined with gas chromatography-olfactometry technology. The results showed that 70 compounds including α-methylbenzyl alcohol (isomer of β-phenylethanol) were identified as odorants. Among them, 39 compounds such as linalool and geraniol showed a high degree of aroma contribution. Furthermore, the Feller's additive model was used to explore the perceptual interactions among the methyl salicylate and the floral compounds (10 groups): five groups of binary compounds showed masking effect after mixing, one group showed additive effect, and four groups showed synergistic effect. The ratio (R) was compared with the aroma index (n) of Steven's law, which found a high-fitness exponential relationship. The results of this study help to provide additional and new theoretical guidance for improving the aroma quality of black tea.

Kombucha: A review of substrates, regulations, composition, and biological properties

Kombucha has been gaining prominence around the world and becoming popular due to its good health benefits. This beverage is historically obtained by the tea fermentation of Camellia sinensis and by a biofilm of cellulose containing the symbiotic culture of bacteria and yeast (SCOBY). The other substrates added to the C. sinensis tea have also been reported to help kombucha production. The type as well as the amount of sugar substrate, which is the origin of SCOBY, in addition to time and temperature of fermentation influence the content of organic acids, vitamins, total phenolics, and alcoholic content of kombucha. The route involved in the metabolite biotransformation identified in kombucha so far and the microorganisms involved in the process need to be further studied. Some nutritional properties and benefits related to the beverage have already been reported. Antioxidant and antimicrobial activities and antidiabetic and anticarcinogenic effects are some of the beneficial effects attributed to kombucha. Nevertheless, scientific literature needs clinical studies to evaluate these benefits in human beings. The toxic effects associated with the consumption of kombucha are still unclear, but due to the possibility of adverse reactions occurring, its consumption is contraindicated in infants and pregnant women, children under 4-years-old, patients with kidney failure, and patients with HIV. The regulations in place for kombucha address a number of criteria, mainly for the pH and alcohol content, in order to guarantee the quality and safety of the beverage as well as to ensure transparency of information for consumers.

Green, Black and Rooibos Tea Inhibit Prostaglandin E2 Formation in Human Monocytes by Inhibiting Expression of Enzymes in the Prostaglandin E2 Pathway

The formation of prostaglandin E2 (PGE2) is associated with adverse inflammatory effects. However, long-term treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) comes with risk of severe side effects. Therefore, alternative ways to inhibit PGE2 are warranted. We have investigated the effects of tea extracts and the polyphenols epigallocatechin gallate (EGCG) and quercetin on PGE2 formation, determined by immunoassay, and protein expression, determined by immunoblotting, of cytosolic phospholipase A2 (cPLA2), cyclooxygenase 2 (COX-2) and microsomal PGE synthase-1 (mPGES-1) in human monocytes. Green and black tea extracts, and with a lower potency, Rooibos tea extract, inhibited lipopolysaccharide (LPS) and calcium ionophore-induced PGE2 formation. In addition, all tea extracts inhibited the LPS-induced expression of mPGES-1, and the green and black tea extracts also inhibited, to a lesser extent, COX-2 expression. The tea extracts only marginally reduced cPLA2 expression and had no effect on COX-1 expression. EGCG, present in green and black tea, and quercetin, present in all three teas, also inhibited PGE2 formation and expression of mPGES-1, COX-2 and cPLA2. Cell-based and cell-free assays were also performed to evaluate direct effects on the enzymatic activity of COX and PGE synthases. Mainly, the cell-free assay demonstrated partial inhibition by the tea extracts and polyphenols. However, the inhibition required higher doses compared to the effects demonstrated on protein expression. In conclusion, green and black tea, and to a lesser extent Rooibos tea, are potent inhibitors of PGE2 formation in human monocytes, and mediate their effects by inhibiting the expression of the enzymes responsible for PGE2 formation, especially mPGES-1.

Enhancement of Cluster Differentiation Antigen 4 and the Body Mass Index in Patients with HIV

&lt;b&gt;Background and Objective:&lt;/b&gt; The HIV is the virus that can cause AIDS by attacking white blood cells such as T cells CD4&lt;sup&gt;+&lt;/sup&gt;. This study aimed to determine the relationship between antiretroviral (ARV) drugs and supplements of black tea (&lt;i&gt;Camellia sinensis&lt;/i&gt; var. &lt;i&gt;assamica&lt;/i&gt;) powder to increase the CD4 and Body Mass Index (BMI) in patients with HIV. &lt;b&gt;Materials and Methods:&lt;/b&gt; This study used a quasi-experiment. From the average number of 10 patient visits every month in the period of January to March, 2021 in the outpatient clinic for patients diagnosed positive with HIV-AIDS, seventy patients were enlisted and divided into 2 groups from 12 districts, 35 groups intervention received ARV drugs and supplements steeping black tea powder form as much as 1,505 mg, equivalent to 5-7 glasses a 1,000-1,400 mL/day for 24 weeks, while the control group of patients received ARV drugs, standard diet each house and nutrition education. &lt;b&gt;Results:&lt;/b&gt; This study showed a BMI before the intervention control group's 1st week 19.31±2.17 and after the intervention for 24 weeks, a BMI of 18.78±2.42. CD4 levels before the intervention, the 1st week were 380.57±78.63 and after the intervention for 24 weeks, 365.74±81.13 in this case either BMI or CD4 did not experience significant improvements. While the intervention group before the intervention 1st week BMI was 21.61±3.32 and after the intervention for 24 weeks, 22.2±3.19 or increased significantly (p = 0.002) and the levels of CD4 in the 1st week before the intervention, 360.91±221.20 and after the intervention for 24 weeks, 425.14±178.87 or increased significantly (p = 0.003). &lt;b&gt;Conclusion:&lt;/b&gt; The ARV therapy and black tea powder significantly increased levels of CD4 and BMI HIV sufferers through the improvement of the status of T-cell immunity and body mass index.

Black Tea Alleviates Particulate Matter-Induced Lung Injury via the Gut-Lung Axis in Mice

Black tea, as the most consumed kind of tea, is shown to have beneficial effects on human health. However, its impact on particulate matter (PM) induced lung injury and the mechanisms involved have been sparsely addressed. Here, we show that PM-exposed mice exhibited oxidative stress and inflammation in the lungs, which was significantly alleviated by a daily intake of black tea infusion (TI) in a concentration-dependent manner. Interestingly, both the ethanol-soluble fraction (ES) and the ethanol precipitate fraction (EP) exhibited better effects than those of TI; moreover, EP tended to have stronger protection than ES in some indicators, implying that EP played a dominant role in the prevention effects. Furthermore, fecal microbiota transplantation (FMT) revealed that the gut microbiota was differentially reshaped by TI and its fractions were able to directly alleviate the injury induced by PMs. These results indicate that daily intake of black tea and its fractions, especially EP, may alleviate particulate matter-induced lung injury via the gut-lung axis in mice. In addition, the Lachnospiraceae_NK4A136_group could be the core gut microbe contributing to the protection of EP and thus should be further studied in the future.

Effect of Black Tea Consumption on Urinary Risk Factors for Kidney Stone Formation

Copious fluid intake is the most essential nutritional measure in the treatment of urolithiasis, and is suggested to be a protective factor in the primary prevention of urinary stone formation. Although the intake of black tea contributes to daily fluid intake, the high oxalate content could outweigh the beneficial effect of urine dilution. The present study investigated the effect of black tea consumption on urinary risk factors for kidney stone formation. Ten healthy men received a standardized diet for a period of ten days. Subjects consumed 1.5 L/day of fruit tea (0 mg/day oxalate) during the 5-day control phase, which was replaced by 1.5 L/day of black tea (86 mg/day oxalate) during the 5-day test phase. Fractional and 24-h urines were obtained. The intake of black tea did not significantly alter 24-h urinary oxalate excretion. Urinary citrate, an important inhibitor of calcium stone formation, increased significantly, while the relative supersaturation of calcium oxalate, uric acid, and struvite remained unchanged. No significantly increased risk for kidney stone formation could be derived from the ingestion of black tea in normal subjects. Further research is needed to evaluate the impact of black tea consumption in kidney stone patients with intestinal hyperabsorption of oxalate.

Metabolomics Analysis Reveals Four Novel N-Ethyl-2-pyrrolidinone-Substituted Theaflavins as Storage-Related Marker Compounds in Black Tea

Tea market is currently oversupplied, and unsold tea often needs to be properly stored for a period of time. However, the chemical changes occurring in black tea during storage are limitedly understood. In this study, a comprehensive nontargeted and targeted metabolomics approach was used to investigate the dynamic changes in compounds in time-series (0-19 months)-stored black teas. The contents of flavanols, theaflavins (TFs), theasinensins, procyanidins, most phenolic acids, amino acids, quercetin-O-glycosides, and myricetin-O-glycosides decreased during storage, while the contents of N-ethyl-2-pyrrolidinone-substituted flavanols, flavone-C-glycosides, and most kaempferol-O-glycosides increased. More importantly, four novel compounds strongly positively correlated with storage duration (r = 0.922-0.969) were structurally assigned as N-ethyl-2-pyrrolidinone-substituted TFs and validated with synthetic reactions of TFs and theanine standards. The content of N-ethyl-2-pyrrolidinone-substituted TFs was 51.54 μg/g in black tea stored for 19 months. To the best of our knowledge, N-ethyl-2-pyrrolidinone-substituted TFs were discovered in tea for the first time.