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

Alternative medicines in oncology: a focus on natural products against gastric cancer

There is justification for optimism about the potential contribution of alternative medicines to cancer management, which now ranks as the second leading cause of death globally. Primary carcinogens arise from several sources, including agriculture, industry, and dietary intake. Gastric cancer (GC) significantly affects an individual's health due to its classification as a malignant tumor associated with elevated mortality and morbidity rates. Chemotherapy is now widely regarded as the gold standard for treating GC. Chemotherapy, however, exerts significant detrimental effects on human health, including irreversible damage to multiple organs. Consequently, it is essential to employ innovative strategies for cancer prevention. Natural products are now the focus of intensive study due to their efficacy against cancer and low toxicity levels. Natural compounds have shown a diverse range of anti-cancer properties. This review aims to emphasize studies on natural compounds that inhibit metastasis, induce apoptosis in GC, and decrease cellular proliferation. All the natural compounds from different sources were incorporated in this review not only medicinal plants derived compounds. This review aims to examine a comprehensive array of natural therapies that may enhance human health and facilitate GC prevention without inducing discernible negative effects. Moreover, this review aims to discuss the toxic side effects of phytochemicals and shed light on mechanisms underlying the action of potential natural products against GC. This review offers a novel perspective by integrating a broad spectrum of natural compounds from diverse sources, not limited to medicinal plants, to explore their anti-cancer properties against gastric cancer.

Encapsulation Efficiency of Electrosprayed Glucose Oxidase Capsules: Effect of the Drying Technique

Glucose oxidase (GOX) is widely used in bakery applications to improve dough rheology and bread quality. However, its direct addition to formulations limits its functionality due to premature enzymatic activity. This study used electrospraying to encapsulate GOX using chia mucilage and sodium alginate as biopolymeric wall materials. Three drying methods-critical point drying (CPD), Lyophilization/freeze-drying (LC), and oven drying (OD)-were compared to evaluate their impact on encapsulation efficiency (EE), enzymatic activity retention, and microstructural integrity. Our findings reveal that CPD preserved the porous structure of the microcapsules, minimizing enzymatic leakage and yielding the highest EE (70%). In contrast, LC induced ice crystal formation, disrupting the polymer network and leading to a moderate EE (27.43%), whereas OD resulted in extensive capsule shrinkage, causing significant enzyme loss (57.1%). The release kinetics of GOX during mixing were best described by the Korsmeyer-Peppas model (R2 = 0.999), indicating a non-Fickian diffusion mechanism influenced by polymer relaxation. These results demonstrate that drying technique selection plays a crucial role in encapsulated enzymes' stability and release behavior, providing new insights for optimizing enzyme delivery in bakery applications.

The Manufacturing Process of Lotus (Nelumbo Nucifera) Leaf Black Tea and Its Microbial Diversity Analysis

Lotus leaves combine both edible and medicinal properties and are rich in nutrients and bioactive compounds. In this study, the lotus leaf tea was prepared using a black tea fermentation process, and the functional components and microbial changes during fermentation were investigated. The results indicated that the activity of polyphenol oxidase showed an initial rise followed by a decline as fermentation progressed, peaked at 3 h with 1.07 enzyme activity units during fermentation. The lotus leaf fermented tea has high levels of soluble sugars (20.92 ± 0.53 mg/g), total flavonoids (1.59 ± 0.05 mg GAE/g), and total polyphenols (41.34 ± 0.87 mg RE/g). Its antioxidant activity was evaluated using ABTS, DPPH, and hydroxyl radical scavenging assays, with results of 18.90 ± 1.02 mg Vc/g, 47.62 ± 0.51 mg Vc/g, and 17.58 ± 1.06 mg Vc/g, respectively. The microbial community also shifted during fermentation. Fusarium played a significant role during the fermentation process. This study demonstrated that the black tea fermentation process improved the functional components and biological activity of lotus leaf tea by optimizing the synergistic effect of enzymatic oxidation and microbial fermentation. The findings not only realized the comprehensive utilization of lotus leaf resources but also provided a foundation for developing innovative functional beverages with enhanced bioactive properties.

Effect of Four Different Initial Drying Temperatures on Biochemical Profile and Volatilome of Black Tea

BACKGROUND

Black tea processing conditions significantly affect the final taste and flavor profiles, so researchers are now focusing on developing equipment and improving the appropriate processing conditions of major black tea varieties.

METHODS

Here, we tested the effect of four different initial drying temperatures, i.e., R65 (65 °C), R85 (85 °C), R105 (105 °C), and R125 (125 °C), on the sensory and biochemical profiles and volatilome of the black tea variety "Lishui wild" (LWV).

RESULTS

Our results indicate that both 85 and 105 °C are better than 65 and 125 °C for initial drying for 20 min. R105 had the highest sensory evaluation scores due to better shape, aroma, taste, leaf base, thearubigins, theanine, caffeine, and ratio of theaflavins + thearubigins to theaflavins. Both R85 and R105 had higher catechins than R65 and R125. The LWV volatilome consisted of esters (19.89%), terpenoids (18.95%), ketones (11.3%), heterocyclic compounds (9.99%), and alcohols (8.59%). In general, acids, aldehydes, amines, aromatics, ethers, hydrocarbons, phenols, sulfur compounds, and terpenoids accumulated in higher amounts in R85 and R105. The highly accumulated compounds in R105 were associated with green, fruity, sweet, woody, floral, hawthorn, mild, nutty, powdery, rose, and rosy flavors. The main pathways affected are secondary metabolites, sesquiterpenoid and triterpenoid biosynthesis, glycerolipid metabolism, zeatin biosynthesis, phenylpropanoid biosynthesis, ABC transport, glutathione metabolism, etc. Therefore, R105 can be used to achieve the optimal taste, flavor, and aroma of LWV.

CONCLUSIONS

Overall, the presented data can be used by the tea industry for processing black tea with the most optimum volatile substances, catechins, theanine, amino acids, and other compounds.

Chemical Diversity of UK-Grown Tea Explored Using Metabolomics and Machine Learning

BACKGROUND/OBJECTIVES

Dartmoor Estate Tea plantation in Devon, UK, is renowned for its unique microclimate and varied soil conditions, which contribute to the distinctive flavours and chemical profiles of tea. The chemical diversity of fresh leaf samples from various garden locations was explored within the plantation.

METHODS

Fresh leaf, which differed by location, cultivar, time of day, and variety, was analysed using Flow Infusion Electrospray Ionisation Mass Spectrometry (FIE-MS).

RESULTS

Random forest classification revealed no significant differences between Georgian N2 cultivar garden locations. However, a significant degree of variability was observed within four tri-clonal variants (Tocklai Variety) with TV9 exhibiting greater similarity to the Georgian N2 cultivar compared to TV8 and TV11, while TV11 was found to be most like TV1. The intraclass variability in leaf composition was similar between the varieties. We explored the metabolic changes over the day in one variant (Camellia assamica Masters), yielding a model with a significant R2 value of 0.617 (p < 0.01, 3000 permutations). Starch and sucrose metabolism was found to be significant where the abundance of these chemical features increased throughout the day and then began to decrease at night.

CONCLUSIONS

This research highlights the complex interplay of cultivars, geographical location, and temporal factors on the chemical composition of tea. It provides insightful data on the metabolic pathways influencing tea cultivation and production and underscores the importance of these variables in determining the final chemical profile and organoleptic characteristics of tea products.

Phytochemicals and Biological Properties of Azorean Camellia sinensis Black Tea Samples from Different Zones of Tea Plantation

Camellia sinensis tea has received considerable attention due to its beneficial effects on health, particularly due to its antioxidant properties that are affected by several factors, which have a high influence on the final quality of black tea. The objective of this study was to investigate the biological properties of Azorean C. sinensis black tea from five different zones of tea plantation in order to select specific areas to cultivate tea rich in targeted compounds beneficial to human health. The free radical scavenging activity (FRSA), ferric reducing antioxidant power (FRAP), ferrous ion chelating (FIC) activities, total phenolic content (TPC), total flavonoid content (TFC), and tannins were determined by colorimetric methods, and catechin and theaflavin contents were analyzed by high-pressure liquid chromatography. The results indicated that samples from Zone E (341 m above the sea level) presented higher values of FRSA (EC50 = 7.22 µg/mL), FRAP (EC50 = 9.06 µg/mL), and FIC activities (79.83%) and higher values of total phenolics (264.76 mg GAE/g DE) and almost all catechins. For TFC, the values were very similar between zones, and for theaflavins content, Zone A showed the best levels, followed by Zone E. In general, these results clearly highlight that altitude plays a significant role in enhancing certain compounds of tea, thereby influencing its quality.

A modern scientific perspective on the flavor and functional properties of diverse teas in traditional cuisine "tea-flavored fish": From macroscopic quality to microscopic variations

The historical appreciation of tea dates back to ancient times, while technological limitations have long hindered in-depth exploration of its flavor complexity and functional attributes. This study investigated the effects of various teas on a traditional delicacy, "tea-flavored fish", using teas processed via traditional methods. Analysis of functional components revealed that processing and fermentation reduced catechin levels (186.3 mg/g to 58.8 mg/g) while increasing theaflavins (16.6 mg/g to 39.6 mg/g), leading to decreased antioxidant and antimicrobial activities. Tea flavored fish was prepared following traditional techniques. The results indicated that the teas preserved their sensory qualities such as texture and color, inhibited metabolic activity and microbial growth, delayed lipid oxidation and protein degradation, and inhibited biogenic amine accumulation. Furthermore, minor compositional variations were observed in the final product. These findings offer novel insights into the application of modern scientific concepts to elucidate the principles underlying traditional craftsmanship.

Comparison of Untargeted and Markers Analysis of Volatile Organic Compounds with SIFT-MS and SPME-GC-MS to Assess Tea Traceability

Tea is one of the most consumed beverages in the world and presents a great aromatic diversity depending on the origin of the production and the transformation process. Volatile organic compounds (VOCs) greatly contribute to the sensory perception of tea and are excellent markers for traceability and quality. In this work, we analyzed the volatile organic compounds (VOCs) emitted by twenty-six perfectly traced samples of tea with two analytical techniques and two data treatment strategies. First, we performed headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) as the most widely used reference method for sanitary and quality controls of food. Next, we analyzed the samples with selected-ion flow-tube mass spectrometry (SIFT-MS), an emerging method for direct analysis of food products and aroma. We compared the performances of both techniques to trace the origin and the transformation processes. We selected the forty-eight most relevant markers with HS-SPME-GC-MS and evaluated their concentrations with a flame ionization detector (FID) on the same instrument. This set of markers permitted separation of the origins of samples but did not allow the samples to be differentiated based on the color. The same set of markers was measured with SIFT-MS instrument without success for either origin separation or color differentiation. Finally, a post-processing treatment of raw data signals with an untargeted approach was applied to the GC-MS and SIFT-MS dataset. This strategy allowed a good discrimination of origin and color with both instruments. Advantages and drawbacks of volatile profiles with both instruments were discussed for the traceability and quality assessment of food.

Withering and Fermentation Affect the Transformation and Accumulation of Key Metabolites in Rougui (Camellia sinensis) for the Formation of Special Taste Characteristics

During the production of Wuyi rock tea, withering and fermentation play a crucial role in the primary processing of the tea, greatly influencing the development of its distinct taste characteristics. In this study, Rougui (Camellia sinensis) was selected as the research object to investigate the effects of withering and fermentation on metabolites and taste characteristics in tea leaves. The findings revealed that a total of 1249 metabolites were detected in Rougui leaves at various processing stages, of which only 40 key metabolites were significantly altered. The process of withering and fermentation is crucial to increase the content of organic acids, plumerane, alkaloids, nucleotides and derivatives, amino acids and derivatives, and free fatty acids in the leaves of Rougui and to decrease the content of saccharides, phenolic acids, flavonols, flavones, and flavanols, which in turn enhances the mellowness, fresh and brisk taste, and aroma of tea and attenuates the saccharides, bitterness, and astringency. Withering and fermentation had the greatest effect on the bitterness and astringency of Rougui taste characteristics, followed by mellowness. It can be seen that withering and fermentation were extremely important for the development of Rougui's special taste characteristics. The present study provides important support for optimizing Rougui processing and the formation of its special taste characteristics.

Determination of Geographical Origin of Southern Shaanxi Congou Black Teas Using Sensory Analysis Combined with Gas Chromatography-Ion Mobility Spectrometry

Southern Shaanxi is one of China's high-quality congou black tea production areas. However, the differences in geography, cultivation, and management techniques and production processes lead to uneven qualities of southern Shaanxi congou black tea in different production areas. This study used sensory analysis combined with gas chromatography-ion mobility spectrometry (GC-IMS) to determine southern Shaanxi congou black teas' geographical origin and volatile fingerprints to prevent economic losses caused by fraudulent labeling. A total of 61 volatile compounds were identified and quantified by GC-IMS. Three main aroma types were found by sensory analysis coupled with significant difference analysis, and a clear correlation between volatile compounds, aroma type, and geographical origin was found by sensory and gallery plot analysis. The black tea with a green/grassy-roast aroma type was mainly distributed in production areas with an altitude of 400-800 m and 1-pentanol, cyclohexanone, 1-penten-3-one, 2-heptanone, dihydroactinidiolide and butyrolactone were the key aroma markers. The black teas produced in production areas with an altitude of 800-1000 m mainly presented strong honey and caramel-like aromas, and sotolone, furaneol, and phenylacetaldehyde played an important role. These results will be helpful for discriminating black tea from different tea production areas in southern Shaanxi.

Study on metabolic variation reveals metabolites important for flavor development and antioxidant property of Hainan Dayezhong black tea

To illustrate the development of chemical properties and characteristic flavor of Hainan Dayezhong black tea, the tea shoots under various manufacturing process were sampled and applied to targeted/widely-targeted metabolomic, transcriptomic, chemometric, and electronic sensory determinations. Totally, 2419 metabolites were identified in this study, of which 20 metabolites were selected as the biomarkers, mainly including amino acids, lipids, and pyrimidine derivatives. The metabolomic-transcriptomic integrated analysis indicated carbon fixation, flavonoid biosynthesis and amino acid metabolism were the major metabolic pathways over manufacturing process of Hainan Dayezhong black tea. The targeted metabolomic detection indicated the accumulations of free amino acids and reduction of total catechins, flavonol glycosides collectively contributed to the development of black tea taste; additionally, the antioxidative properties were decreasing along the production process. These results suggest that the tradeoff between bioactivity components and antioxidative capacity contribute to the characteristic flavor of Hainan Dayezhong black tea.

Dynamic Changes in Aroma Compounds during Processing of Flat Black Tea: Combined GC-MS with Proteomic Analysis

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.

Exploring the ancient roots and modern global brews of tea and herbal beverages: A comprehensive review of origins, types, health benefits, market dynamics, and future trends

Tea, a culturally significant beverage, originated around 2700 B.C. in ancient Chinese civilization, with a profound understanding of its therapeutic properties. Herbal medicines from diverse plant sources have been esteemed for their phytochemical content. Today, tea's appeal spans the globe, with various processing techniques creating distinct tea varieties. This review article comprehensively explores tea and herbal teas, encompassing their origins, types, trade history, health benefits, chemical composition, and market and future dynamics. This review examines tea's evolution from ancient China to its global significance and analyzes the impact of tea trade routes on cultural exchanges and trade dynamics. The review covers conventional teas (black, green, and oolong), blended teas, and herbal teas. It primarily focuses on herbal beverages' chemical composition and active components derived from diverse plants and botanicals, highlighting their traditional uses and health-promoting applications. The review provides valuable insights into the dynamic herbal tea market, growth, consumer preferences, industry trends, and future aspects of the herbal beverage. Additionally, it explores the proper classification and preparation of herbal drinks for maximum benefits, shedding light on tea manufacturing and preparation processes. This review is a valuable resource for tea enthusiasts, health-conscious individuals, and industry stakeholders, offering profound insights into teas and their multifaceted allure.

Antioxidant Scavenging of the Superoxide Radical by Yerba Mate (Ilex paraguariensis) and Black Tea (Camellia sinensis) Plus Caffeic and Chlorogenic Acids, as Shown via DFT and Hydrodynamic Voltammetry

We describe the antioxidant capability of scavenging the superoxide radical of several tea and yerba mate samples using rotating ring-disk electrochemistry (RRDE). We directly measured superoxide concentrations and detected their decrease upon the addition of an antioxidant to the electrochemical cell. We studied two varieties of yerba mate, two varieties of black tea from Bangladesh, a sample of Pu-erh tea from China, and two components, caffeic acid and chlorogenic acid. All of these plant infusions and components showed strong antioxidant activities, virtually annihilating the available superoxide concentration. Using density functional theory (DFT) calculations, we describe a mechanism of superoxide scavenging via caffeic and chlorogenic acids. Superoxide can initially interact at two sites in these acids: the H4 catechol hydrogen (a) or the acidic proton of the acid (b). For (a), caffeic acid needs an additional π-π superoxide radical, which transfers electron density to the ring and forms a HO2- anion. A second caffeic acid proton and HO2- anion forms H2O2. Chlorogenic acid acts differently, as the initial approach of superoxide to the catechol moiety (a) is enough to form the HO2- anion. After an additional acidic proton of chlorogenic acid is given to HO2-, three well-separated compounds arise: (1) a carboxylate moiety, (2) H2O2, and a (3) chlorogenic acid semiquinone. The latter can capture a second superoxide in a π-π manner, which remains trapped due to the aromatic ring, as for caffeic acid. With enough of both acids and superoxide radicals, the final products are equivalent: H2O2 plus a complex of the type [X-acid-η-O2], X = caffeic, chlorogenic. Chlorogenic acid (b) is described by the following reaction: 2 O2•- + 2 chlorogenic acid → 2 chlorogenic carboxylate + O2 + H2O2, and so, it acts as a non-enzymatic superoxide dismutase (SOD) mimic, as shown via the product formation of O2 plus H2O2, which is limited due to chlorogenic acid consumption. Caffeic acid (b) differs from chlorogenic acid, as there is no acidic proton capture via superoxide. In this case, approaching a second superoxide to the H4 polyphenol moiety forms a HO2- anion and, later, an H2O2 molecule upon the transfer of a second caffeic acid proton.

Mechanisms of intestinal pharmacokinetic natural product-drug interactions

The growing co-consumption of botanical natural products with conventional medications has intensified the need to understand potential effects on drug safety and efficacy. This review delves into the intricacies of intestinal pharmacokinetic interactions between botanical natural products and drugs, such as alterations in drug solubility, permeability, transporter activity, and enzyme-mediated metabolism. It emphasizes the importance of understanding how drug solubility, dissolution, and osmolality interplay with botanical constituents in the gastrointestinal tract, potentially altering drug absorption and systemic exposure. Unlike reviews that focus primarily on enzyme and transporter mechanisms, this article highlights the lesser known but equally important mechanisms of interaction. Applying the Biopharmaceutics Drug Disposition Classification System (BDDCS) can serve as a framework for predicting and understanding these interactions. Through a comprehensive examination of specific botanical natural products such as byakkokaninjinto, green tea catechins, goldenseal, spinach extract, and quercetin, we illustrate the diversity of these interactions and their dependence on the physicochemical properties of the drug and the botanical constituents involved. This understanding is vital for healthcare professionals to effectively anticipate and manage potential natural product-drug interactions, ensuring optimal patient therapeutic outcomes. By exploring these emerging mechanisms, we aim to broaden the scope of natural product-drug interaction research and encourage comprehensive studies to better elucidate complex mechanisms.

Metagenomic, organoleptic profiling, and nutritional properties of fermented kombucha tea substituted with recycled substrates

Kombucha fermentation yields a diverse range of beneficial macro and micronutrients. In our study, we examined the metabolites, antioxidant activity, organoleptic characteristics, and nutritional attributes of traditionally prepared kombucha tea, using black tea and sugar (control) as substrates, and compared them with tea made from tea dust and blackstrap molasses (test). Kombucha tea crafted from functional raw materials exhibited enhanced sensory qualities and improved health-promoting properties. The levels of tannins, flavonoids, and phenols play a crucial role in determining the antioxidant activity of kombucha tea. Using the DPPH and FRAP methods, we investigated the antioxidant activity throughout the fermentation period, ranging from day 0 to day 12, under optimized conditions. The results consistently demonstrated an initial increase in antioxidant activity from day 0 to 6, followed by a decline from day 6 to 12. Notably, statistical analysis revealed that the antioxidant activity of the test sample was significantly better (p > 0.001) compared to the control sample. The nutritional content of the kombucha from day 6 of the test sample is higher than the control sample provided sugars (fructose 0.4 ± 0.1, glucose 0.7 ± 0.1, sucrose 1.4 ± 0.1) g/100 mL, minerals (calcium, 19.4 ± 0.15, iron 23.1 ± 0.25, and potassium 28.3 ± 0.25) mg/100 mL, vitamins (B1 0.58 ± 0.01, B2 0.30 ± 0.02, B3 0.33 ± 0.02, B6 0.75 ± 0.02, B9 0.19 ± 0.03, B12 0.9 ± 0.03, and C 1.38 ± 0.06) mg/100 mL, sodium 4.35 ± 0.25 mg/100 mL, calories 14.85 ± 0.25 mg/100 mL, carbohydrates 3.135 ± 0.12, and acids (acetic acid 4.20 ± 0.02, glucuronic acid 1.78 ± 0.02) mg/100 mL on day 12. The predominant microbial species identified in both control and test samples included Komagataeibacter rhaeticus, Gluconobacter oxydans, Brettanomyces bruxellensis, and Zygosaccharomyces bailli, each with varying dominance levels. These microorganisms play essential roles in metabolizing sugars, generating acids, and contributing to the distinctive flavor profile of kombucha. Sensory evaluations of the control and test samples were analyzed, and the overall preference was 88% for the test sample with tea dust and molasses. The sensory characteristics of the test sample included a fruity smell (41%), fizzy texture (66%), bright color (47%), and a fruity taste (67%), with overall acceptability (56%) rating it as excellent. Our research contributes to a deeper understanding of the interplay between raw materials, microbial composition, and the resulting composition of bioactive compounds.

Understanding and exploring the diversity of soil microorganisms in tea (Camellia sinensis) gardens: toward sustainable tea production

Leaves of Camellia sinensis plants are used to produce tea, one of the most consumed beverages worldwide, containing a wide variety of bioactive compounds that help to promote human health. Tea cultivation is economically important, and its sustainable production can have significant consequences in providing agricultural opportunities and lowering extreme poverty. Soil parameters are well known to affect the quality of the resultant leaves and consequently, the understanding of the diversity and functions of soil microorganisms in tea gardens will provide insight to harnessing soil microbial communities to improve tea yield and quality. Current analyses indicate that tea garden soils possess a rich composition of diverse microorganisms (bacteria and fungi) of which the bacterial Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes and Chloroflexi and fungal Ascomycota, Basidiomycota, Glomeromycota are the prominent groups. When optimized, these microbes' function in keeping garden soil ecosystems balanced by acting on nutrient cycling processes, biofertilizers, biocontrol of pests and pathogens, and bioremediation of persistent organic chemicals. Here, we summarize research on the activities of (tea garden) soil microorganisms as biofertilizers, biological control agents and as bioremediators to improve soil health and consequently, tea yield and quality, focusing mainly on bacterial and fungal members. Recent advances in molecular techniques that characterize the diverse microorganisms in tea gardens are examined. In terms of viruses there is a paucity of information regarding any beneficial functions of soil viruses in tea gardens, although in some instances insect pathogenic viruses have been used to control tea pests. The potential of soil microorganisms is reported here, as well as recent techniques used to study microbial diversity and their genetic manipulation, aimed at improving the yield and quality of tea plants for sustainable production.

Using QuEChERS and HPLC Method to Monitor the Background Concentration of Polycyclic Aromatic Hydrocarbons in Commercial Black Tea Leaves and Infusions in Taiwan

Tea is an integral part of Taiwanese culture and is a popular drink as it contains many beneficial compounds. However, during the processing of tea, polycyclic aromatic hydrocarbons (PAHs) may form. This study investigated the concentrations of PAH4 in different black tea leaves and tea infusions based on the origin of the tea. The samples were extracted using QuEChERS, while the content of PAH4 was analyzed by high performance liquid chromatography coupled to a fluorescence detector (HPLC-FLD). The content of PAH4 in the tea leaves ranged from 2.88 µg/kg to 218.2 µg/kg (dry weight), with the highest concentration being found in teas from Vietnam. The concentration of BaP ranged from ND to 47.92 µg/kg. The release of PAH4 from tea leaves to tea infusions was significantly low, with the highest transfer being 25.8%. In this study, all PAH4 compounds in commercial black tea leaves can be detected by QuEChERS extraction with a simple HPLC method.