Non-targeted and targeted metabolomics profiling of tea plants (Camellia sinensis) in response to its intercropping with Chinese chestnut

BACKGROUND

Intercropping is often used in the tea producing areas where land resources are not so abundant, and the produced green tea is tasted more delicious through a tea-Chinese chestnut intercropping system according to the experience of indigenous farmers. The length and weight of tea leaf increase under this intercropping system and their root systems are stratified vertically and coordinate symbiosis. However, the delicacy mechanism under the intercropping is not fully understood.

RESULTS

Green tea from the Chinese chestnut-tea intercropping system established in the 1980s ranked highest compared with a pure tea plantation from the same region. Based on the non-targeted metabolomics, 100 differential metabolites were upregulated in the tea leaves from intercropping system relative to monoculture system. Twenty-one amino acids were upregulated and three downregulated in response to the intercropping based on the targeted metabolomics; half of the upregulated amino acids had positive effects on the tea taste. Levels of allantoic acid, sugars, sugar alcohols, and oleic acid were higher and less bitter flavonoids in the intercropping system than those in monoculture system. The upregulated metabolites could promote the quality of tea and its health-beneficial health effects. Flavone and flavonol biosynthesis and phenylalanine metabolism showed the greatest difference. Numerous pathways associated with amino acid metabolism altered, suggesting that the intercropping of Chinese chestnut-tea could greatly influence amino acid metabolism in tea plants.

CONCLUSIONS

These results enhance our understanding of the metabolic mechanisms by which tea quality is improved in the Chinese chestnut-tea intercropping system and demonstrate that there is great potential to improve tea quality at the metabolomic level by adopting such an intercropping system.

Exogenous melatonin improves tea quality under moderate high temperatures by increasing epigallocatechin-3-gallate and theanine biosynthesis in Camellia sinensis L

Global warming has multifarious effects on crop growth and productivity. Nonetheless, the effects of moderate-high temperatures and melatonin on tea yield and quality remain unclear. In this study, we found that melatonin, a universal growth stimulatory molecule, not only promotes photosynthesis and biomass accumulation in tea plants (Camellia sinensis L.) but also improves tea quality under sub high temperature (SHT). SHT increased the dry biomass and photosynthesis by 40.8% and 28.1%, respectively, and exogenous melatonin caused a further improvement. Moreover, SHT increased the total polyphenol concentrations and decreased the free amino acid concentrations, leading to a significant increase (68.2%) in polyphenol to free amino acid ratio. However, melatonin decreased the polyphenol to free amino acid ratio by delicately improving the concentrations of polyphenols and amino acids. Consistent with the total polyphenol, melatonin increased the concentrations of (-)-catechin, (-)-gallocatechin (GC), and (-)-epigallocatechin-3-gallate (EGCG) in tea leaves. The qRT-PCR analysis revealed that melatonin increased the transcript levels of catechins biosynthesis genes, such as CsCHS, CsCH1, CsF3H, CsDFR, CsANS, CsLAR, and CsANR under SHT. Meanwhile, the theanine concentration was decreased by SHT, which was attributed to the attenuated expression of CsGS, CsGOGAT, CsGDH, and CsTS1. Nonetheless, melatonin significantly increased those transcripts and the content of theanine under SHT. Melatonin also increased the caffeine content by inducing the expression of CsTIDH, CssAMS, and CsTCS1. These results suggest that melatonin could positively alter tea growth and quality by modulating the photosynthesis and biosynthesis of polyphenols, amino acids, and caffeine in tea leaves under SHT.

Exploration of a Method of Distinguishing Different Nongxiang Tieguanyin Tea Grades Based on Aroma Determined by GC-MS Combined with Chemometrics

An aroma-based method for distinguishing different grades of Nongxiang Tieguanyin was explored by taking special grade (K110) and 1-4 grades (K101, K102, K103, and K104) of this tea as samples. Tea samples were analyzed by gas chromatography-mass spectrometry (GC-MS) combined with chemometrics. Results showed differences in the types and relative contents of aroma components among different grades of Nongxiang Tieguanyin tea. In the principal component analysis (PCA) scoring plot, except for K102 and K103, tea samples of different grades were distributed in different regions. Components satisfying variable important for the projection (VIP) > 1 and peak areas with significant differences (p < 0.05) among different tea grades were screened. Finally, 18 differential variables were screened out from 143 volatiles. The clustering results of these variables were consistent with those of PCA. K102 and K103 were initially clustered into one group and then clustered with K101, K110, and K104 in turn. The clear PCA separation of these samples and uniform hierarchical cluster analysis (HCA) clustering results suggests that GC-MS coupled with chemometrics analysis is a valid and accurate approach for discriminating different grades of Nongxiang Tieguanyin. The screened differential variables could represent a difference in aroma quality among five grades of Nongxiang Tieguanyin tea. Clear rules between peak area and the grade were also observed in some differential variables. 1-Ethylpyrrole and unknown-32 were positively correlated with grade. 2-Methylfuran, 2-ethylfuran, 2-methylidenecyclopentan-1-ol, mesityl oxide, 2-amylfuran, and D-limonene were negatively correlated with grade. The peak areas of methyl acetate, dimethyl sulfide, 6-methylhept-5-en-2-one, and (Z)-β-ocimene initially decreased but then increased with declining grade. The toluene content was especially high in K104 but only a negligible difference was observed among other grades. This study provides a potential method for differentiating Nongxiang Tieguanyin teas of different grades based on aroma. Unknown samples could be classified by comparison of their spatial distribution with those of known standard samples in PCA or HCA, as well as the peak area differences of differential variables between unknown samples and known standard samples.

Improved Protocols of ITS1-Based Metabarcoding and Their Application in the Analysis of Plant-Containing Products

Plants are widely used for food and beverage preparation, most often in the form of complex mixtures of dried and ground parts, such as teas, spices or herbal medicines. Quality control of such products is important due to the potential health risks from the presence of unlabelled components or absence of claimed ones. A promising approach to analyse such products is DNA metabarcoding due to its high resolution and sensitivity. However, this method’s application in food analysis requires several methodology optimizations in DNA extraction, amplification and library preparation. In this study, we present such optimizations. The most important methodological outcomes are the following: (1) the DNA extraction method greatly influences amplification success; (2) the main problem for the application of metabarcoding is DNA purity, not integrity or quantity; and (3) the “non-amplifiable” samples can be amplified with polymerases resistant to inhibitors. Using this optimized workflow, we analysed a broad set of plant products (teas, spices and herbal remedies) using two NGS platforms. The analysis revealed the problem of both the presence of extraneous components and the absence of labelled ones. Notably, for teas, no correlation was found between the price and either the absence of labelled components or presence of unlabelled ones; for spices, a negative correlation was found between the price and presence of unlabelled components.

Challenges in Developing Analytically Validated Laboratory-Derived Dietary Supplement Databases

The Dietary Supplement Label Database (DSLD) is sponsored by the Office of Dietary Supplements (ODS) and the National Library of Medicine (NLM). It provides a searchable, free database of the contents of ∼65,000 supplement labels. A companion database of analytically verified product labels [the Dietary Supplement Ingredient Database (DSID)] was created by ODS, NLM, and the USDA. There are considerable challenges to populating both databases, but the DSID faces unique analytic chemistry challenges. This article describes the challenges to creating analytically verified marketplace surveys of dietary supplement (DS) product content claims for inclusion in public databases. Nutritionists and public health scientists require information on actual exposures to DS constituents because labeled content may not match labeled product content. Analytic verification of composition of DSs provides a link to actual exposure. A public database of analytically derived DS content was developed to provide more accurate estimates of dietary intake in population-based epidemiologic studies. The DSID has conducted surveys of several types of vitamin- and mineral-containing DSs. Results showing label content claims as analytically derived values are available in the current DSID. A recent pilot project explored the feasibility of adding botanical DS products to the DSID. Candidates for future botanical DSID studies will be based on sales volume, potential public health impacts, and the availability of validated analytic methods and reference materials. Databases like DSID and the DSLD are essential for researchers and clinicians to evaluate dietary ingredient intakes in population-based epidemiologic studies. Together, these databases provide a picture of the DS marketplace. The DSID provides an analytic survey of marketed DSs. However, selection of future botanical supplements for DSID evaluation involves analytic challenges. Even when appropriate resources are available, method selection and data evaluation are resource- and time-consuming.

Differentiation of key biomarkers in tea infusions using a target/nontarget gas chromatography/mass spectrometry workflow

Climatic conditions affect the chemical composition of edible crops, which can impact flavor, nutrition and overall consumer preferences. To understand these effects new data analysis software capable of tracking hundreds of compounds across years of samples under various environmental conditions is needed. Our recently developed mass spectral (MS) subtraction algorithms have been used with spectral deconvolution to efficiently analyze complex samples by 2-dimensional gas chromatography/mass spectrometry (GC-GC/MS). In this paper, we address the accuracy of identifying target and nontarget compounds by GC/MS. Findings indicate that Yunnan tea contains higher concentrations of floral compounds. In contrast, Fujian tea contains higher concentrations of compounds that exhibit fruity characteristics, but contains much less monoterpenes. Principal components analysis shows that seasonal changes in climate impact tea plants similarly despite location differences. For example, spring teas contained more of the sweet, floral and fruity compounds compared to summer teas, which had higher concentrations of green, woody, herbal compounds.

Effects of brewing conditions on the phytochemical composition, sensory qualities and antioxidant activity of green tea infusion: A study using response surface methodology

Green tea is a highly consumed beverage, and the phytochemical composition, sensory qualities, and antioxidant activity of tea infusion are significantly affected by brewing conditions. However, the simultaneous effects of brewing conditions on the infusion are unknown. This study aimed to model the effects of brewing conditions (temperature, time, water/tea ratio and particle size) on the phytochemical composition, sensory profiles and antioxidant activity of green tea infusion using response surface methodology. The regression models describing the brewing of detected indexes were significant (p ≤ 0.01) and reliable (R² ≥ 0.854). Particle size had the greatest negative effects on the phytochemical composition and antioxidant activities of tea infusion. Optimization of brewing conditions performed for five types of needs and preferences for consuming were verified to be credible. In particular, optimal conditions of overall acceptance were 82 °C (temperature), 5.7 min (time), 70 mL/g (water/tea ratio), and 1100 µm (particle size).

Occurrence of acrylamide carcinogen in Arabic coffee Qahwa, coffee and tea from Saudi Arabian market

The present work describes the outcomes of the assessment on acrylamide contents in a number of thermally treated foods (Arabic coffee Qahwa, coffee and tea) obtained from the Saudi Arabian markets. A total of 56 food samples of different brands and origin were studied, the amounts of acrylamide in Arabic coffee Qahwa, coffee and tea were obtained in the range of 10 to 682 μg kg-1. In comparison to coffee (152-682 μg kg-1), the Arabic coffee Qahwa (73-108 μg kg-1) and tea (10-97 μg kg-1) contain lower amounts of acrylamide. Among the analyzed samples, the green tea contained low amounts of acrylamide ranged from 10 to 18 μg kg-1, and thus the green tea could be considered as a healthier hot drink. A great variation of acrylamide formation has been observed in these food products. This divergence may be due to the initial concentration of amino acids especially asparagines and reducing sugars in food products, in addition to roasting temperature and time, pH and water activity. The obtained data can also be used in epidemiological investigation to estimate the acrylamide exposure from nutritional survey.

Recent Advances in Volatiles of Teas

Volatile compounds are important components of tea aroma, a key attribute of sensory quality. The present review examines the formation of aromatic volatiles of various kinds of teas and factors influencing the formation of tea volatiles, including tea cultivar, growing environment and agronomic practices, processing method and storage of tea. The determination of tea volatiles and the relationship of active-aroma volatiles with the sensory qualities of tea are also discussed in the present paper.

Flavor characteristics of seven grades of black tea produced in Turkey

Seven grades of black tea [high-quality black tea (grades 1-3) and low-quality black tea (grades 4-7)], processed by ÇAYKUR Tea Processing Plant (Rize, Turkey), were compared for their differences in descriptive sensory analysis (DSA), aroma-active compounds (volatile compounds), and taste-active compounds (sugar, organic acid, and free amino acid compositions). Ten flavor attributes such as 'after taste', 'astringency', 'bitter', 'caramel-like', 'floral/sweet', 'green/grassy', 'hay-like', 'malty', 'roasty', and 'seaweed' were identified. Intensities for a number of flavor attributes ('after taste', 'caramel-like', 'malty', and 'seaweed') were not significantly different (p > 0.05) among seven grades of black tea. A total of 57 compounds in seven grades of black tea (14 aldehydes, eight alcohols, eight ketones, two esters, four aromatic hydrocarbons, five aliphatic hydrocarbons, nine terpenes, two pyrazines, one furan, two acids, and two miscellaneous compounds) were tentatively identified. Of these, aldeyhdes comprised more than 50% to the total volatile compounds identified. In general, high-grade quality tea had more volatiles than low-grade quality tea. With respect to taste-active compounds, five sugars, six organic acids, and 18 free amino acids were positively identified in seven grades of black tea, of which fructose, tannic acid, and theanine predominated, respectively. Some variations (p < 0.05), albeit to different extents, were observed among volatile compounds, sugars, organic acids, and free amino acids in seven grades of black tea. The present study suggests that a certain flavor attributes correlate well with taste- and aroma-active compounds. High- and low-quality black teas should not be distinguished solely on the basis of their DSA and taste- and aroma-active compounds. The combination of taste-active compounds together with aroma-active compounds renders combination effects that provide the characteristic flavor of each grade of black tea.

Simultaneous determination of seven bioactive components in Oolong tea Camellia sinensis: quality control by chemical composition and HPLC fingerprints

A simple and reliable method of high-performance liquid chromatography (HPLC) was developed for the quality control of oolong tea (the dry leaves of Camellia sinensis ): the quality control included the HPLC fingerprint and the quantitative determination of seven bioactive compounds chemicals, namely, (-)-gallocatechin, (-)-epigallocatechin, (-)-epigallocatechin gallate, caffeine, (-)-epicatechin, gallocatechin gallate, and (-)-epicatechin gallate. The developed analyses of the chemicals excelled in quantifying the chemicals in oolong tea. The chemical fingerprint of oolong tea was established using the raw materials of three main production sites in China, that is, Fujian (southern and northern parts), Taiwan, and Guangdong. The fingerprints from different cultivated sources were analyzed by hierarchical cluster analysis, similarity analysis, principal component analysis (PCA), analysis of variance (ANOVA), and discriminant analysis. The results indicated that the combination of chromatographic fingerprint and quantification analysEs could be used for the quality assessment of oolong tea and its derived products.

Pu-erh tea tasting in Yunnan, China: correlation of drinkers' perceptions to phytochemistry

AIM OF THE STUDY

Pu-erh (or pu'er) tea tasting is a social practice that emphasizes shared sensory experience, wellbeing, and alertness. The present study examines how variable production and preparation practices of pu-erh tea affect drinkers' perceptions, phytochemical profiles, and anti-oxidant activity.

MATERIALS AND METHODS

One hundred semi-structured interviews were conducted in Yunnan Province to understand the cultural and environmental context of pu-erh tea tasting. The gong fu cha dao ('way of tea' with 'effort,' 'work,' or 'skill') method of brewing tea through multiple infusions was employed to evaluate green and black pu-erh samples from smallholder agro-forests and terrace plantations. Ranking interviews, High Performance Liquid Chromatography (HPLC), and the 1-1-diphenyl-2-picrylhydrazyl (DPPH) assay were conducted to characterize color and taste profiles, Total Catechin Content (TCC), Total Methylxanthine Content (TMC), and free radical scavenging capacity (IC(50)).

RESULTS

Significant variation was found among pu-erh samples based on: (1) agro-ecosystem mode of production by TCC (P<0.0001) and TMC (P<0.0265), (2) processing method for TCC (P<0.0001), TMC (P<0.0027), and free radical scavenging capacity (P<0.0001), (3) infusion sequence for TMC (P<0.0013), (4) taste rankings for TCC (P<0.0001), TMC (P<0.0001), and IC(50) (P<0.0059) and, (5) color rankings for TMC (P<0.0009) and IC(50) (P<0.0001). Samples rated as bitter and bitter-sweet contained the greatest TCC and free radical scavenging capacity.

CONCLUSIONS

This research demonstrated that production environment, processing methods, and infusion sequence in preparing tea are related to the phytochemical profile, free radical scavenging activity, and flavor of tea. Findings contribute to the ethnomedical literature by supporting previous studies that have hypothesized that the taste of plants, particularly bitterness, may guide societies in the search for medicinal plants and beneficial phytochemicals.

Exposure and risk assessment for aluminium and heavy metals in Puerh tea

As the consumption of Puerh tea is booming because of its multiple health-promoting effects, the possible health risks resulting from long-term exposure to metals contained in this tea need to be evaluated. To assess the human risk associated with drinking Puerh tea, concentrations of aluminium, lead, cadmium, mercury, zinc, copper and arsenic were determined in samples of Puerh tea, tea leaves from the plants, and planted soil collected from the Yunnan province, China. Site-specific exposure parameters such as body weight and consumption rate of Puerh tea were investigated in Kunming and Puer cities using face-to-face surveys. Health risks were evaluated for the inhabitants of Kunming and Puer cities by gender and by age groups. Although the Puerh tea plant easily absorbs aluminium from soil, the concentrations of Al and six other elements in Puerh tea were all far below the safety concentration limits of China. Both the HQ (Hazard Quotient) values for single elements and the HI (Hazard Index) value for all seven elements were far below one, indicating no non-carcinogenic risks from these seven elements for inhabitants of Kunming and Puer under the current consumption rates of Puerh tea. However, probabilistic estimation of carcinogenic risk shows that the 95th percentile carcinogenic rate of arsenic in Puerh tea approaches the accepted risk level of 10(-4) for the highest exposure group. Therefore, the arsenic in Puerh tea is of concern.

[Contents of flavonoids, tannins and fiber in some species of vegetative tea]

The content of some biologically active substances such as flavonoids, tannins and soluble dietary fiber in various types of vegetative tea was analyzed. The results are shown that the content of flavonoids ranges from 0.28 to 9.87%, tannins--from 0.91 to 7.07% and soluble dietary fiber 0.37 up to 14.7%.

[Content of heavy metals in various kinds of loose-leaf tea]

The content of heavy metals--lead, cadmium, mercury, arsenicum was studied in 7 kinds of tea. Lead was detected practically in all studied kinds of tea, except for self-drinking long-lenved tea Sri-Lanka, cadmium was detected in Chinese Green coarse-grained tea, arsenicum was detected in all kinds of tea. However heavy metals content in all studied kinds of tea doesn't exceed their maximum allowable concentration.

Effect of girdling on levels of catechins in fresh leaf in relation to quality of 'Huang Zhi Xiang' Oolong' tea

Oolong tea is one of the most popular beverages due to the presence of significant amount of catechins. Experiments were conducted to investigate the effect of girdling treatment on levels of catechins in fresh tea leaf related to quality of the 'Huang Zhi Xiang' Oolong tea (Camellia sinensis). The variations in the levels of catechins in fresh tea leaf and the quality score (QS) of the 'Huang Zhi Xiang' Oolong tea were examined. The study demonstrated that girdling treatment increased significantly the levels of (-)-epicatechin, (-)-epigallocatechin, (-)-epigallocatechin gallate, (-)-epicatechin gallate, total catechins, simple catechin, and catechin gallate present in fresh leaf of tea trees. Furthermore, the girdling treatment improved significantly the quality of the 'Huang Zhi Xiang' Oolong tea. Thus, it was suggested that application of girdling treatment could be an effective agronomic practice to increase the quality of 'Huang Zhi Xiang' Oolong tea.

Pesticide usage pattern in tea ecosystem, their retrospects and alternative measures

Tea is a perennial plantation crop grown under monoculture providing favorable conditions for a variety of pests. The concept of pest control has undergone a considerable change over the past few decades. In recent years there has been a greater dependence on the use of pesticides (7.35-16.75 kgha(-1)) with little importance laid on other safe control methods for the management of tea pests. Due to this practice, the tea pests showed a higher tolerance/ resistance status due to formation of greater amount of esterases, glutathione S-transferase and acetylcholinesterase. Thus, over reliance on pesticides end up with pesticide residue in made tea (DDT - 10.4-47.1%; endosulfan - 41.1-98.0%; dicofol- 0.0-82.4%; ethion - 0.0-36.2%; cypermethrin - 6.0- 45.1%). The growing concern about the pesticide residue in made tea, its toxicity hazards to consumers, the spiraling cost of pesticides and their application have necessitated a suitable planning which will ensure a safe, economic as well as effective pest management in tea. At present it is a global concern to minimize chemical residue in tea and European union and German law imposed stringent measures for the application of chemicals in tea and fixed MRL values at < or = 0. 1 mgkg(-1) for the most commonly used pesticides which will not be met out in the real practice and has been a major constraint to tea exporting countries like India. In order to regulate the situation of the Indian market at global level, central insecticide board and prevention of food adulteration regulation committee have reviewed the MRL position for tea and has recommended 10 insecticides, 5 acaricides, 9 herbicides and 5 fungicides for use in tea and issued the tea distribution and export control order 2005 which will help the country to limit the presence of undesirable substances in tea. This review attempts to provide the readers with a comprehensive account of pesticide use in North East in tea, surveillance report of the European community regarding the residue level in Assam and Darjeeling tea, recent amendments by international and national regulatory bodies, revised MRL values of pesticides in tea, an update about the current strategies for the management of tea pests with more focus on the use of biological control agents and a possible beneficial role or judicious use of chemical pesticides in complement with other alternative measures to achieve optimum effects in terms of limiting agricultural input, lowering production costs, reducing environmental contamination and the effect on non-target organisms, delaying the development of resistant pest biotypes and above all minimizing the pesticide residues in tea to increase the exports.

Prediction of Japanese green tea ranking by fourier transform near-infrared reflectance spectroscopy

A rapid and easy determination method of green tea's quality was developed by using Fourier transform near-infrared (FT-NIR) reflectance spectroscopy and metabolomics techniques. The method is applied to an online measurement and an online prediction of green tea's quality. FT-NIR was employed to measure green tea metabolites' alteration affected by green tea varieties and manufacturing processes. A set of ranked green tea samples from a Japanese commercial tea contest was analyzed to create a reliable quality-prediction model. As multivariate analyses, principal component analysis (PCA) and partial least-squares projections to latent structures (PLS) were used. It was indicated that the wavenumber region from 5500 to 5200 cm(-1) had high correlation with the quality of the tea. In this study, a reliable quality-prediction model of green tea has been achieved.

Chemical profiling and gene expression profiling during the manufacturing process of Taiwan oolong tea "Oriental Beauty"

Oriental Beauty, which is made from tea leaves infested by the tea green leafhopper (Jacobiasca formosana) in Taiwan, has a unique aroma like ripe fruits and honey. To determine what occurs in the tea leaves during the oolong tea manufacturing process, the gene expression profiles and the chemical profiles were investigated. Tea samples were prepared from Camellia sinensis var. sinensis cv. Chin-shin Dah-pang while the tea leaves were attacked by the insect. The main volatile compounds, such as linalool-oxides, benzyl alcohol, 2-phenylethanol, and 2,6-dimethylocta-3,7-diene-2,6-diol, increased during manufacture. The gene expression profiles during manufacture were analyzed by differential screening between fresh leaves and tea leaves of the first turn over. Many up-regulated transcripts were found to encode various proteins homologous to stress response proteins. Accordingly, the endogenous contents of abscisic acid and raffinose increased during manufacture. Thus the traditional manufacturing method is a unique process that utilizes plant defense responses to elevate the production of volatile compounds and other metabolites.

[Study on the identification of tea using near infrared reflectance spectroscopy]

A rapid tea identification method by near infrared spectroscopy coupled with pattern recognition based on principal components analysis and Mahalanobis' distance technique was proposed. Four famous brand teas in China were studied, including Longjing tea, Biluochun tea, Maofeng tea and Tieguanyin tea in the experiment. In the spectral region between 6 500 and 5 300 cm(-1), through preprocessing method of MSC (multiplicative scatter comection), the prediction model was built. The result showed that the model was the best with 8 principal component factors. The rates of identification in calibration set samples and prediction set samples were 98.75% and 95%, respectively. A new idea about quick and precise identification of tea was offered.

Yield and quality responses of citrus (Citrus reticulate) and tea (Podocarpus fleuryi Hickel.) to compound fertilizers

Experiments were carried out with citrus (Citrus reticulate) and tea (Podocarpus fleuryi Hickel.) to study the effects of compound fertilizers on their yields and quality. In the citrus experiment, application of compound fertilizers increased available P, K and Mg contents in soil but decreased alkali-hydrolyzable N contents in soil and N, P and K contents in leaves. In the tea experiment, application of compound fertilizers increased available P, K and Mg contents in soil and N, P, K and Mg contents in leaves but decreased alkali-hydrolyzable N in soil compared with the urea treatment. Application of compound fertilizers could improve the quality of citrus and tea, increase their yields and enhance their economical profits significantly. Compared with the control, application of compound fertilizers increased citrus yields by 6.31, 12.94 and 17.69 t/ha, and those of tea by 0.51, 0.86 and 1.30 t/ha, respectively. Correspondingly, profits were increased by 21.4% to 61.1% for citrus and by 10.0% to 15.7% for tea. Optimal rates of compound fertilizers were recommended for both crops.

[Determination of nine life elements in brick tea by ICP-AES]

ICP-AES was used for the direct determination of nine life elements (Ca, Mg, K, Al, P, Cu, Zn, Fe and Mn) in brick tea. The RSDs of the method were between 2.11% and 8.68%, and the analytical results of the tea reference samples were consistent with the certified values. The method was simple and accuracy. The analytical results of brick tea were compared with those of the ordinary leaf tea (green tea, scent tea and oolong tea). The Al, Fe, Mn, Ca and Mg contents of brick tea were about 5.78, 3.26, 2.19, 2.11 and 1.64 times higher than those of the ordinary leaf tea respectively. The P, K, Zn and Cu contents of brick tea were 48.70%, 85.68%, 78.19% and 98.78% times lower than those of the ordinary leaf tea respectively.

Variations of main quality components of tea genetic resources [Camellia sinensis (L.) O. Kuntze] preserved in the China National Germplasm Tea Repository

The variations of the main quality components of tea, tea polyphenols, catechins, amino acids, caffeine, and water extract of 596 accessions Chinese tea genetic resources, preserved in the China National Germplasm Tea Repository (CNGTR), were analyzed. Tea polyphenols content on a dry weight basis varied from 13.6 to 47.8%, averaging 28.4%. The tea polyphenols content increases gradually from northern and eastern provinces to southern provinces, the highest is in Yunnan tea resources. The content of catechins ranged from 81.9 g/kg to 262.7 g/kg, averaging 144.6 g/kg. The genetic resources from Hunan province had the highest catechins content, inconsistent with the tea polyphenols, which were highest in Yunnan tea resources. The amino acids content ranged from 1.1 to 6.5%, with an average of 3.3%. It was much lower in the southern provinces compared with northern and eastern provinces. The average caffeine content was 4.2%, varying from 1.2 to 5.9%. Yunnan province has plentiful high caffeine genetic resources, next is Fujian province. Caffeine content of Chinese and Japanese tea genetic resources were very similar. The average of water extract content was 44.7%, varying from 24.4 to 57.0%. The variation pattern was similar to that of tea polyphenols. Tea genetic resources of transnormal components are valuable and they could be used directly or indirectly for commercial functional components extract, breeding, and production.

Electronic nose based tea quality standardization

In this paper we have used a metal oxide sensor (MOS) based electronic nose (EN) to analyze five tea samples with different qualities, namely, drier month, drier month again over-fired, well fermented normal fired in oven, well fermented overfired in oven, and under fermented normal fired in oven. The flavour of tea is determined mainly by its taste and smell, which is generated by hundreds of Volatile Organic Compounds (VOCs) and Non-Volatile Organic Compounds present in tea. These VOCs are present in different ratios and determine the quality of the tea. For example Assamica (Sri Lanka and Assam Tea) and Assamica Sinesis (Darjeeling and Japanese Tea) are two different species of tea giving different flavour notes. Tea flavour is traditionally measured through the use of a combination of conventional analytical instrumentation and human or ganoleptic profiling panels. These methods are expensive in terms of time and labour and also inaccurate because of a lack of either sensitivity or quantitative information. In this paper an investigation has been made to determine the flavours of different tea samples using an EN and to explore the possibility of replacing existing analytical and profiling panel methods. The technique uses an array of 4 MOSs, each of, which has an electrical resistance that has partial sensitivity to the headspace of tea. The signals from the sensor array are then conditioned by suitable interface circuitry. The data were processed using Principal Components Analysis (PCA), Fuzzy C Means algorithm (FCM). We also explored the use of a Self-Organizing Map (SOM) method along with a Radial Basis Function network (RBF) and a Probabilistic Neural Network classifier. Using FCM and SOM feature extraction techniques along with RBF neural network we achieved 100% correct classification for the five different tea samples with different qualities. These results prove that our EN is capable of discriminating between the flavours of teas manufactured under different processing conditions, viz. over-fermented, over-fired, under fermented, etc.

Fungi associated with black tea and tea quality in the Sultanate of Oman

Forty-eight samples of four popular commercial brands of black tea (Camellia sinensis L.) were purchased from the local markets in Muscat area, Sultanate of Oman. Tea leaves were surveyed for mycoflora. Five fungal species were isolated with A. niger as the most dominant in all the brands having percentage contamination ranging between 0.66% and 30.34%. Other fungi isolated were Aspergillusflavus, Penicillium spp. and Pacelomyces spp. but having average percentages of 0.6%, 0.84% and 0.21% respectively. Significant differences were found among the batches contaminated by A. niger. None of the 25 A. flavus strains screened for aflatoxins were found aflatoxigenic. The total ash, water-soluble ash, and mineral concentration of the samples were within the British standards and were not affected by fungal contamination. The results showed that black tea is contaminated by fungi that might constitute health hazards for humans. The post harvest contamination of tea could be eliminated or reduced if processing is conducted under more hygienic conditions.

Tea and cancer prevention: an evaluation of the epidemiologic literature

Animal and in vitro studies provide evidence of an anticarcinogenic potential of active ingredients in teas. This review encompasses epidemiologic studies of stomach, colon, and lung cancer as well as the evidence of a relationship between tea drinking and cancer at large in humans. Cohort studies do not suggest a protective role for tea drinking in the total risk of cancer. Site-specific studies reveal a more complex picture. The epidemiologic studies on tea drinking and stomach cancer do not justify claims of a cancer-protective effect. A protective effect of green tea on the development of colon cancer is suggested. The evidence regarding black tea is less clear, with some indication of a risk of colon or rectal cancer associated with regular use of black tea. The studies on tea and lung cancer also suggest an increased risk with increased tea consumption. The range and crude categorization of tea consumption, choice of control groups, and inadequate control for confounding might have obscured possible relationships. From the limited studies that suggest a favorable effect from tea, it is likely that benefits are restricted to high intakes in high-risk populations.

New aspects on the chemistry of tea and coffee. A short review

Recent publications (1982/1983) on the chemistry and technology of tea (leaf, green and black) and coffee (raw, roasted and instant), in particular with respect of their composition and changes during manufacture and storage, and the effects of composition on the quality of the beverages, are reviewed (101 references).

The biochemistry and technology of tea manufacture

This review surveys tea-production technology, chemistry of raw and manufactured tea as well as tea tasting appraisal and chemical analysis of manufactured tea. The paper describes the healthful properties of tea, gives general information on the tea plant and manufactured tea, and presents classification of teas as related to the processing of black green, yellow, and red tea, green pressed tea as well as instant tea and tea dyes. The paper discusses the chemical composition of raw and manufactured tea as well as approaches to the evaluation of tea quality--tea tasting appraisal and chemical analysis. The paper is supplied with the conclusions and references. The section on the healthful properties of tea discusses various aspects of catechin effects--vitamin P, antimicrobial, antioxidative and radioprotective effects. Also described are favorable effects of tea alkaloids--caffeine, theobromine, theophylline that dilatate cerebral vessels and alleviate headaches. The section on the production of different teas (black, green, yellow, red, instant teas, and tea dyes) considers technological methods and biochemical bases of various types of tea manufacture. The role of tea leaf enzymes in the oxidative processes determining the tea quality is discussed in detail. This section also describes the contribution of thermochemical processes into the formation of tea flavor. The compounds dictating tea taste and aroma are discussed, particularly tannins and catechins, volatile oils, nitrogen compounds, and some other substances.