Trace elements in tea leaves, made tea and tea infusion: A review

2014-2016 seasonal rainfall effects on metals in tea (Camelia sinensis (L.) Kuntze)

Plant-climate interactions affect the edible crop composition, impacting flavor, nutrition, and overall consumer liking. In this study, principal components analysis was used to assess the macro- and micronutrient metal concentrations in pre-monsoon (spring), monsoon (summer), and post-monsoon (autumn) tea (Camelia sinensis (L.) Kuntze) from Yunnan Province, China in 2014-2016. Statistical differences were observed (p = 1.35E-24). Fe, Ca, Mg, Mn, Al, and Ba concentrations were higher in June (monsoon) than in March (pre-monsoon) and September (post-monsoon) compared to Pb, K, Cu, Zn, and Na, which were higher in March and September. Although Fe, Ca, Mg, Mn, Al, and Ba concentrations increased during the monsoon season, sensory analysis did not detect metallic taste in either minimally processed or farmer-processed (commercial) teas. This finding shows the seasonal differences in flavor were due to striking differences in organic chemical composition and concentration.

A strategic analysis of tea leaves supply chain before manufacturing – a case in Assam

Purpose

There exists insufficient literature on classification and taxonomy of tea leaves supply chain (TLSC), so the purpose of this paper is to study the existing TLSCs and classify them accordingly. Apart from this, the paper also focuses on identification of key decisions issues in the supply chains (SC) and developing a TLSC decision framework for the state of Assam in India.

Design/methodology/approach

The paper is based on a two-year detailed study on TLSC in Assam which encompasses 22 Tea Estates, 41 Small Tea Gardens (STGs) and a Research Institute (Tocklai Tea Research Institute). Secondary data were collected from relevant websites of various government organizations of India, company’s websites, annual reports, official statements from the companies, tea market reports, annual reports of the Indian Tea Association, the Tea Board of India, Tea Research Institute and published reports, etc.

Findings

The “point of origin” of TLSC is a tea garden, “point of consumption” is considered as a tea factory and green tea leaves (GTLs) forms the basic raw material. This SC includes mainly three players: Tea leaves growers, manufacturers of made tea and tea leaves agents. This study identifies the three types of TLSCs existing in Assam: TLSC1, TLSC2 and TLSC3. Among them, only TLSC1 is both responsive as well as an efficient chain, while the rest are only responsive chains. Later two SCs can be made efficient with the proposed TLSC4.

Research limitations/implications

There is an insufficient literature on classification and taxonomy of TLSC, therefore the study (considerably the classification and taxonomy of TLSC) was developed from the primary data which were collected from the 22 Tea Estates and 41 STGs of four districts of Assam, because of limited time (two years). The study should have involved more tea estates and small tea gardens for better classification and taxonomy.

Practical implications

The proposed model suggests that small tea growers may create a co-operative whereby smaller tea gardens (STGs) (members of the co-operative) unite to act as a single large garden, set up their own co-operative factory and recruit permanent tea plucking laborers. This up-gradation of TLSC2 and TLSC3 to TLSC4 may enable a group of STGs to work in a manner similar to a Tea Estate.

Originality/value

To the best of authors’ knowledge this is one of the first studies to classify the TLSC in Assam.

Magnetic solid-phase extraction of pyrethroid insecticides from tea infusions using ionic liquid-modified magnetic zeolitic imidazolate framework-8 as an adsorbent

A MSPE-GC-MS/MS method was developed for the analysis of pyrethroids from tea infusions using Fe₃O₄/ZIF-8/IL as an adsorbent.

Voltammetric determination of aluminum(III) as Al-Alizarin S complex in tea leaves and infusions

This work presents, for the first time, DPV methodology of indirect aluminum (III) determination in tea leaves and infusions using the renewable silver amalgam electrode. A self-referencing strategy was proposed which relies on alternate voltammetric curves registration with and without conditioning of the electrode surface. The developed procedure utilizing formation of aluminum-Alizarin S complex shows linearity in the range of 2-50 μg L^-1 of Al(III) concentration, with r > 0.997. In the case of the electrode conditioning LOD is 0.2 μgL^-1 and repeatability expressed by CV is 1-2%. Introducing an additional operation i.e. electrode activation results in decrease of sensitivity from 0.0162 to 0.0043 μA/μgL^-1. The method was verified using CRM (tea leaves). Due to the wide variety of tea origin, types and producers, four most popular sorts (black, green, red and white) were chosen, made by one manufacturer. It was demonstrated that the proposed methodology may be applied in Al(III) determination in tea leaves and infusions. Al(III) extraction effectiveness was also examined. It was verified, that lemon juice addition during brewing increases aluminum concentration in infusions. Using Principal Components Analysis it was demonstrated that automatic distinction of infusions brewed with and without lemon juice, based on unprocessed voltammetric signal, may be successfully realized.

Metal concentrations in traditional and herbal teas and their potential risks to human health

Food and beverage consumption is an important route for human exposure to metals. Traditional tea (Camellia sinensis) is a widely-consumed beverage, which may contain toxic metals. This study determined total and infusion concentrations of 5 metals including Al, As, Cd, Cr, and Pb in 47 traditional and herbal teas from 13 countries and assessed their potential risks to human health. The data showed that herbal teas exhibited higher As (0.26mgkg^-1), Cd (0.19mgkg^-1) and Pb (2.32mgkg^-1) than traditional teas. Black tea from India had high Cr at 31mgkg^-1 while white tea from China had low Cr at 0.39mgkg^-1. Arsenic, Cd and Pb did not exceed the WHO limit for medicinal plants excluding one herbal tea with 1.1mgkg^-1 As and 26.4mgkg^-1 Pb. However, Cr in 47% herbal teas and 73% traditional teas exceeded the Canada limit of 2mgkg^-1. Metal concentrations in tea infusions were below the MCL for drinking water except for Al. Total Al and its infusion was lower in herbal teas (47-1745mgkg^-1 and 0.09-3.95mgL^-1) than traditional teas (50.3-2517mgkg^-1 and 0.02-7.51mgL^-1), with 0.9-22% and 4-49% of the Al being soluble in infusion. The Al concentrations in infusion in all black tea and 83, 75 and 25% of the green, oolong and herbal teas exceeded the secondary MCL for drinking water at 0.2mgL^-1. However, the weekly intake of Al from drinking tea (0.001-0.39 and 0.003-0.56mgkg^-1 for children and adults) was lower than the provisional tolerable weekly intake for Al at 1.0mgkg^-1. Our data showed that it is important to consider metal intake from tea consumptions, especially for Cr and Al in heavy tea drinkers.

Synthesis of NiO nanoparticles via a green route using Monsonia burkeana: The physical and biological properties

NiO nanoparticles have emerged as ideal candidates in various fields due to their magnetic, electrical and optical properties. The coupling of plant extracts that have anticancer and antibacterial properties with NiO nanoparticles has increased their usage in the biomedical field. In this work, we report on the novel synthesis of NiO nanoparticles using a local medicinal plant, Monsonia burkenea. The nickel nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), Energy dispersive X-ray analysis (EDX), Scanning electron microscope (SEM), High-resolution transmission electron microscope (HRTEM) and X-ray diffraction (XRD). FTIR showed that the extraction of the plant phytochemicals was successful and the green synthesized nanoparticles from plants contained the phytochemical groups that are found in the Monsonia burkeana plant. XRD and HRTEM confirmed the successful formation of NiO nanoparticles with an average particle size range of 20 nm. These results were also corroborated by elemental mapping and EDX, where the dominant groups were identified.The Monsonia burkeana NiO particles exhibited selective bactericidal activity against Gram-negative strains, such as E. coli and P. aeruginosa. Additionally, cytotoxicity studies showed the materials did not have any anti proliferative effect against A549 lung cancer cells but could be used as potential drug delivery vehicles against human cancers.

Assessment of the Bioaccessibility of Trace Elements in Cat's Claw Teas by In Vitro Simulated Gastrointestinal Digestion Using FAAS

The aim of this study was to evaluate the bioaccessibility of Ca, Fe, Mg, Mn, and Zn in cat's claw plant teas through in vitro gastrointestinal digestion with gastric and intestinal juice solutions. The total concentrations and bioaccessible fractions of Ca, Fe, Mg, Mn, and Zn were measured by flame atomic absorption spectrometry (FAAS). The results obtained showed that Zn was the most bioaccessible element in the teas, contributing a mean of 57.9% by infusion and 62.5% by decoction. Among macroelements, the Ca was less bioaccessible with 17.4% recovery. The bioavailability assessment revealed that daily intake of 200 ml of cat's claw teas cover about 1.0% of manganese RDA.

Heavy metal pollution and health risk assessment of agricultural soils in a typical peri-urban area in southeast China

Heavy metal pollution in peri-urban areas in China is serious and complex. We thus developed an integrated evaluation method to assess heavy metal pollution and potential health risk to residents in a typical peri-urban area with diverse anthropogenic emission sources and cropping systems. Ecological risk was evaluated using Nemerow's synthetical pollution index (P_n) and Potential ecological risk index (RI). Then polluted areas and responsible emission sources were identified by GIS mapping. Health risk caused by food intake and soil exposure was calculated by accounting for the influence of anthropogenic emissions and cropping systems. Agricultural soils in the study area were polluted by cadmium (Cd), mercury (Hg), lead (Pb), and arsenic (As). High concentrations mainly occurred near the mining area and along the roadsides. The accumulation of heavy metals in crops followed the order of tea leaves > rice grain > vegetables. The hazard index of potential human health risk caused by chronic soil exposure and food intake was 15.3, indicating obvious adverse health effects. 87.5% of health risk was attributed to food consumption, and significantly varied among different cropping systems with the decreasing order of rice (10.44) >vegetable (2.86) > tea (0.05). The integrated method of ecological and health risk index, which takes consideration of both anthropogenic emission and cropping system can provide a practical tool for evaluating of agricultural soil in the peri-urban area regrading different risk factors.

Micronutrients (B, Co, Cu, Fe, Mn, Mo, and Zn) content in made tea (Camellia sinensis L.) and tea infusion with health prospect: A critical review

Tea (Camellia sinensis L.) is a perennial acidophilic crop, and known to be a nonalcoholic stimulating beverage that is most widely consumed after water. The aim of this review paper is to provide a detailed documentation of selected micronutrient contents, viz. boron (B), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn) in made tea and tea infusion. Available data from the literature were used to calculate human health aspect associated with the consumption of tea infusion. A wide range of micronutrients reported in both made tea and tea infusion could be the major sources of micronutrients for human. The content of B, Co, Cu, Fe, Mn, Mo, and Zn in made tea are ranged from 3.04 to 58.44 μg g^-1, below detectable limit (BDL) to 122.4 μg g^-1, BDL to 602 μg g^-1, 0.275 to 13,040 μg g^-1, 0.004 to 15,866 μg g^-1, 0.04 to 570.80 μg g^-1 and 0.01 to 1120 μg g^-1, respectively. Only 3.2 μg L^-1 to 7.25 mg L^-1, 0.01 μg L^-1 to 7 mg L^-1, 3.80 μg L^-1 to 6.13 mg L^-1, 135.59 μg L^-1 -11.05 mg L^-1, 0.05 μg L^-1 to 1980.34 mg L^-1, 0.012 to 3.78 μg L^-1, and 1.12 μg L^-1 to 2.32 μg L^-1 of B, Co, Cu, Fe, Mn, Mo, and Zn, respectively, are found in tea infusion which are lower than the prescribed limit of micronutrients in drinking water by World Health Organization. Furthermore, micronutrient contents in tea infusion depend on infusion procedure as well as on the instrument used for analysis. The proportion of micronutrients found in different tea types are 1.0-88.9% for B, 10-60% for Co, 2.0-97.8% for Cu, 67.8-89.9% for Fe, 71.0-87.4% for Mn, 13.3-34% for Mo, and 34.9-83% for Zn. From the results, it can also be concluded that consumption of three cups of tea infusion per day does not have any adverse effect on human health with respect to the referred micronutrients rather got beneficial effects to human.

Effect of teapot materials on the chemical composition of oolong tea infusions

BACKGROUND

The flavor and quality of tea are widely believed to be associated with the pot in which the tea is made. However, this claim is mostly by experiences and lacks solid support from scientific evidence. The current study investigated and compared the chemical compositions of oolong tea made with six different teapot materials, namely Zisha, Zhuni, stainless steel, ceramic, glass and plastic.

RESULTS

For each tea sample, polyphenols and caffeine were examined by HPLC-UV, volatile compounds by GC/MS, amino acids by LC/MS and minerals by ICP-MS. The results suggested that tea infusions from Zisha and Zhuni pots contain higher levels of EGC, EGCG and total catechins and less caffeine than those from ceramic, glass and plastic pots and tend to have the lowest total mineral contents, potassium and volatile compounds in tea soup. The statistical differences were not all significant among Zisha, Zhuni and stainless steel pots.

CONCLUSION

Based on the overall chemical composition of the tea infusion, Yixing clay pots (Zisha and Zhuni) produce tea infusions that are presumably less bitter and more fragrant and tend to contain more healthful compounds than tea infusions from other pots. The results could partially explain why Yixing clay pots are among the most popular teapots. The beneficial effects of long-term repeated use of these teapots warrants further study. © 2017 Society of Chemical Industry.

Paradigm shift of contamination risk of six heavy metals in tea (Camellia sinensis L.) growing soil: A new approach influenced by inorganic and organic amendments

The present study provides several contamination and ecological risk indices for selected metals (Cd, Cr, Cu, Mn, Ni and Zn) in tea (Camellia sinensis L.; cv. S.3A/3) growing soil influenced by lower to higher doses of inorganic and organic amendments. While ecological risk indices were applied, it was observed that same treatment showed different risk levels but contamination risk status did not vary significantly. All the indices showed significant correlation with heavy metals' concentration in young shoots of tea plants. As the indices characterized experimental soils with different extents of contamination, it would be important to standardize the indices with long term experiments followed by generation of new index. Therefore, we formulated a new contamination index named as Tea Research Association Heavy Metal Contamination Index (TRAHMCI) for tea growing soils. TRAHMCI is based on the probable change of metal status in soil with progress of growth of tea plant. This could be useful to negate discrepancies arised from use of various existing metal contamination indices in tea growing soils amended with different doses of fertilizers. TRAHMCI was formulated based on individual contamination factor using statistical technique and applied to the present dataset which provided a more holistic understanding of overall tea growing soil behavior. The limitation of the developed TRAHMCI index is that, the index had not been validated for other crops in our study not to claim its effective use for crops other than tea. As already mentioned, this new index had been formulated by taking tea as the test crop with above mentioned six heavy metal contents in young shoot and made tea.

Multiple origins and a narrow genepool characterise the African tea germplasm: concordant patterns revealed by nuclear and plastid DNA markers

Despite the highly economic value of tea in Africa, its genetic and geographic origins remain largely unexplored. Here we address this by collecting 439 samples across 11 countries in Africa and Asia to investigate the origin and genepool composition of African tea based on 23 nuclear microsatellites loci (nSSRs) and three cpDNA intergenic spacer regions. Our results indicated that the African tea represents a potpourri originating from multiple introductions over time. The nSSR analysis revealed that the majority (79%) of tea accessions collected in Africa belong to Indian Assam tea which have likely originated from India and/or Sri Lanka. The patterns of nSSR variation also showed that Chinese Assam tea is genetically distinct from Indian Assam tea, and has rarely been used in African tea breeding efforts since only 4% of the African tea accessions possessed this genotype. We found a total of 22 cpDNA haplotypes, which grouped into three main geographic clades that were concordant with the distribution of microsatellite genotypes. Several private cpDNA haplotypes were identified in Chinese Assam tea in Southern Yunnan province of China. Therefore Chinese Assam tea will be important for the enrichment of African tea gene pools. Our results is a useful guide in future tea breeding programmes in Africa.

Comparative Assessment of Copper, Iron, and Zinc Contents in Selected Indian (Assam) and South African (Thohoyandou) Tea (Camellia sinensis L.) Samples and Their Infusion: A Quest for Health Risks to Consumer

The current study aims to assess the infusion pattern of three important micronutrients namely copper (Cu), iron (Fe), and zinc (Zn) contents from black tea samples produced in Assam (India) and Thohoyandou (South Africa). Average daily intakes and hazardous quotient were reported for these micronutrients. Total content for Cu, Fe, and Zn varied from 2.25 to 48.82 mg kg^-1, 14.75 to 148.18 mg kg^-1, and 28.48 to 106.68 mg kg^-1, respectively. The average contents of each of the three micronutrients were higher in tea leaves samples collected from South Africa than those from India while the contents in tea infusions in Indian samples were higher than in South African tea samples. Results of this study revealed that the consumption of 600 mL tea infusion produced from 24 g of made tea per day may be beneficial to human in terms of these micronutrients content. Application of nonparametric tests revealed that most of the data sets do not satisfy the normality assumptions. Hence, the use of both parametric and nonparametric statistical analysis that subsequently revealed significant differences in elemental contents among Indian and South African tea.

Healthy properties of green and white teas: an update

Green tea has been consumed for centuries in Japan, China and Morocco.

Improving Risk Assessment Calculations for Traditional Foods Through Collaborative Research with First Nations Communities

As industrial development is increasing near northern Canadian communities, human health risk assessments (HHRA) are conducted to assess the predicted magnitude of impacts of chemical emissions on human health. One exposure pathway assessed for First Nations communities is the consumption of traditional plants, such as muskeg tea (Labrador tea) (Ledum/Rhododendron groenlandicum) and mint (Mentha arvensis). These plants are used to make tea and are not typically consumed in their raw form. Traditional practices were used to harvest muskeg tea leaves and mint leaves by two First Nations communities in northern Alberta, Canada. Under the direction of community elders, community youth collected and dried plants to make tea. Soil, plant, and tea decoction samples were analyzed for inorganic elements using inductively coupled plasma-mass spectrometry. Concentrations of inorganic elements in the tea decoctions were orders of magnitude lower than in the vegetation (e.g., manganese 0.107 mg/L in tea, 753 mg/kg in leaves). For barium, the practice of assessing ingestion of raw vegetation would have resulted in a hazard quotient (HQ) greater than the benchmark of 0.2. Using measured tea concentrations it was determined that exposure would result in risk estimates orders of magnitude below the HQ benchmark of 0.2 (HQ = 0.0049 and 0.017 for muskeg and mint tea, respectively). An HHRA calculating exposure to tea vegetation through direct ingestion of the leaves may overestimate risk. The results emphasize that food preparation methods must be considered when conducting an HHRA. This study illustrates how collaboration between Western scientists and First Nations communities can add greater clarity to risk assessments.

Spent Tea Leaf Templating of Cobalt-Based Mixed Oxide Nanocrystals for Water Oxidation

The facile synthesis of nanostructured cobalt oxides using spent tea leaves as a hard template is reported. Following an impregnation-calcination and template removal pathway, sheetlike structures containing nanosized crystallites of Co₃O₄ are obtained. Co₃O₄ incorporated with Cu, Ni, Fe, and Mn (M/Co = 1/8 atomic ratio) are also prepared, and the materials are thoroughly characterized using X-ray diffraction, electron microscopy, and N₂ sorption. The method is applicable to several commercial tea leaves and is successfully scaled up to prepare over 7 g of Co₃O₄ with the same nanostructure. The oxides are then tested for electrochemical water oxidation, and Cu, Ni, and Fe incorporations show beneficial effect on the catalytic activity of Co₃O₄, achieving performance comparable to levels from benchmark electrocatalysts. These data suggest that tea leaf templating can be utilized as a facile and promising approach to prepare nanostructured functional catalyst.

Analytical Assessment of Bio- and Toxic Elements Distribution in Pu-erh and Fruit Teas in View of Chemometric Approach

This study concerns application of flame atomic absorption spectrometry (FAAS) in assessment of macro- and microelement and toxic metal levels (Mg, Ca, K, Na, Mn, Cu, Fe, Zn, Cr, Ni, Co, Cd and Pb) in dark (Pu-erh) and fruit tea leaves and their infusions. Phosphorus was also determined in the form of phosphomolybdate by spectrophotometric method. The reliability of the method was checked using three certified reference materials. The results of analysis were in agreement with the certified values, with analytical recovery ranging from 86 to 113 %. Significant correlations (p < 0.001) were found between concentrations of P, Zn, K, Ni, Fe, Co, Cr, and Pb in Pu-erh tea, whereas in fruit tea, such interdependences were found between Mg, Fe, P, Ni, and Co. Kruskal-Wallis test results have related differences in Pu-erh tea quality as well as technological processing of fruit tea to their mineral composition. In order to characterize tea elemental content, chemometric techniques such as factor analysis (FA) and cluster analysis (CA) were used. Their application allowed on differentiation of samples in view of the fermentation type, technological processing, and overall quality.

Is there a relationship between tea intake and maternal whole blood heavy metal concentrations?

The aim of this analysis was to examine the association between tea intake during pregnancy and maternal and infant metal exposures. Data from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study, a pan-Canadian pregnancy cohort, were used. All participants with a gestational age of ⩾20 weeks (n=1954) with available biomarkers were included. Geometric means (GMs) for lead, arsenic, mercury, cadmium and manganese in maternal (first and third trimesters) and cord blood, as well as speciated arsenic in maternal urine in the first trimester, were calculated for participants who drank regular, green or herbal tea and for those who did not. Differences between groups were examined using chi-square tests. Adjusted least squares geometric means (LSGMs) were estimated by tea intake, controlling for factors such as country of birth, coffee intake and maternal smoking. Concentrations of all metals were above the limits of detection in most participants in the first trimester: lead (GM): 0.62 μg/dl), mercury (GM: 2.99 nmol/l); cadmium (GM 1.93 nmol/l), arsenic (GM 9.75 nmol/l) and manganese (GM 160.1 nmol/l). Adjusted LSGMs for lead in the first trimester were higher for tea drinkers than for those who were non-tea drinkers (LSGM 0.65 μg/dl, 95%CI: 0.62, 0.69 and 0.61 μg/dl, 95%CI: 0.59, 0.62), and there was evidence of a dose-response relationship for green and herbal tea. Those who consumed herbal tea in the third trimester had significantly higher third trimester maternal and cord blood lead concentrations than non-herbal tea drinkers. This study provides evidence of an association between blood lead concentrations and green or herbal tea consumption. However, the GM blood lead concentrations of the highest tea consumers were still less than 1 μg/dl and within the normal range of blood lead concentrations in the Canadian population.

Transition rates of selected metals determined in various types of teas (Camellia sinensis L. Kuntze) and herbal/fruit infusions

Teas and raw materials used as ingredients of herbal and fruit infusions (HFI) were analysed by means of ICP-MS for their content of aluminium, arsenic, cadmium, copper, lead and mercury in the dry product and in the infusion. Samples of tea (Camellia sinensis L. Kuntze) were selected to include different origins, types (black, green), leaf grades (whole leaf, broken, fannings, dust) and manufacturing techniques (orthodox, "crush, tear, curl"). The selected HFI raw materials (chamomile, elderberries, fennel, hibiscus, mate, peppermint, rooibos and rose hip) cover the most important matrices (flower, fruit, seed, herb, leaf) and reflect the economic significance of these HFI materials in trade. Infusions were prepared under standardised conditions representing typical household brewing. Transition rates for the investigated metals vary significantly but are mostly well below 100%. We propose default transition rates for metals to avoid overestimation of exposure levels from tea/HFI consumption.

Boron and strontium isotope ratios and major/trace elements concentrations in tea leaves at four major tea growing gardens in Taiwan

Isotopic compositions of B and Sr in rocks and sediments can be used as tracers for plant provincial sources. This study aims to test whether tea leaf origin can be discriminated using (10)B/(11)B and Sr isotopic composition data, along with concentrations of major/trace elements, in tea specimens collected from major plantation gardens in Taiwan. The tea leaves were digested by microwave and analyzed by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). The data showed significant variations in (87)Sr/(86)Sr ratios (from 0.70482 to 0.71462), which reflect changes in soil, groundwater or irrigation conditions. The most radiogenic tea leaves were found at the Taitung garden and the least radiogenic ones were from the Hualien garden. The δ (11)B was found to change appreciably (δ (11)B = 0.38-23.73 ‰) which could be due to fertilizers. The maximum δ (11)B was also observed in tea samples from the Hualien garden. Principal component analysis combining (87)Sr/(86)Sr, δ (11)B and major/trace elements results successfully discriminated different sources of major tea gardens in Taiwan, except the Hualien gardens, and this may be due to rather complicated local geological settings.

Risk assessment of mineral and heavy metal content of selected tea products from the Ghanaian market

Food consumption is the most likely route of human exposure to metals. Tea (Camellia sinensis L.) is among the most widely consumed non-alcoholic beverages. Concentrations of heavy metals and minerals in tea from 15 different brands in Kumasi, Ghana were measured to assess the health risk associated with their consumption. The mineral and metal contents (Fe, Cu, Zn, Pb, As, Cd) were analyzed using atomic absorption spectrophotometer (Z-8100 polarized Zeeman). The results revealed that the mean concentrations were in the order: Ca > Fe > As > Cd > Zn > Pb. The average contents of Ca, Fe, Zn, Pb, Cd, and As in the samples were 94.08, 6.15, 0.20, 0.16, 0.36, and 1.66 mg/kg, respectively. All the minerals and heavy metals were below the maximum permissible limits stipulated by the World Health Organization (WHO) and US Pharmacopeia (USP). Metal-to-metal correlation indicated strong correlations between As/Zn, Cd/Zn, Cd/As, and Pb/As pairs. Factor analysis demonstrated a clear separation between minerals, grouped on one side, and heavy metals, clustered on another side. Both the target hazard quotient (THQ) and hazard index (HI) levels in green tea were far below 1, suggesting that consumption of green tea should pose no potential risk to human health. However, carcinogenic risk levels for arsenic were high; R > 10(-6). The results showed that residents in Kumasi consume tea could be at risk from exposure to these heavy metals and minerals.

Rapid determination of trace level copper in tea infusion samples by solid contact ion selective electrode

A new solid contact copper selective electrode with a poly (vinyl chloride) (PVC) membrane consisting of o-xylylenebis(N,N-diisobutyldithiocarbamate) as ionophore has been prepared. The main novelties of constructed ion selective electrode concept are the enhanced robustness, cheapness, and fastness due to the use of solid contacts. The electrode exhibits a rapid (< 10 seconds) and near-Nernstian response to Cu²⁺ activity from 10^-1 to 10^-6 mol/L at the pH range of 4.0-6.0. No serious interference from common ions was found. The electrode characterizes by high potential stability, reproducibility, and full repeatability. The electrode was used as an indicator electrode in potentiometric titration of Cu(II) ions with EDTA and for the direct assay of tea infusion samples by means of the calibration graph technique. The results compared favorably with those obtained by the atomic absorption spectroscopy (AAS).

Monitoring of essential and heavy metals in green tea from different geographical origins

The present study measured the concentrations of toxic metals (Cd, Pb) and other elements (Ca, K, Mg, Na, P, Mn, Fe, Zn, Cu, Co, Cr, Ni) in tea leaves and their infusions. The total metal contents were determined by atomic absorption spectrometry. Phosphorus concentration was determined using an ultraviolet-visible spectrophotometer. Assessment of the mineral composition enabled determination of the leaching percentage and the risk of exceeding provisional tolerable weekly intake for Cd through daily tea consumption. The concentrations of bioelements were analyzed based on the recommended daily intake values for each. According to recently established standards, green tea was found to be a rich source of Mn. The average Pb and Cd levels in a 200-mL beverage were 0.002 and 0.003 mg, respectively. Indian teas had the highest percentage of Cd leaching (43.8%) and Chinese tea had the lowest (9.41%). Multivariate analysis techniques such as factor analysis and cluster analysis were used to differentiate samples according to geographical origin (China, India, or Japan). Potassium, P, Mn, Fe, Cu, Co, and Cd were effective descriptors for the identification of tea samples from China, India, and Japan.

The determination of Fukushima-derived cesium-134 and cesium-137 in Japanese green tea samples and their distribution subsequent to simulated beverage preparation

Health Canada's Radiation Protection Bureau has identified trace quantities of (134)Cs and (137)Cs in commercially available green tea products of Japanese origin. Referenced to March 11, 2011, the activity ratio ((134)Cs/(137)Cs) has been determined to be 1:1, which supports an origin from the Fukushima Dai-ichi Nuclear Power Plant accident. The upper limits of typical tea beverage preparation conditions were applied to the most contaminated of these green tea samples to determine the proportion of radiocesium contamination that would be available for human consumption. The distribution of radiocesium among the components of the extraction experiments (water, residual tea solid, and filter media) was determined by both conventional and Compton-suppressed gamma spectroscopy. The latter aided tremendously in providing a more complete radiocesium distribution profile, particularly for the shorter-lived (134)Cs. Cesium extraction efficiencies of 64 ± 7% and 64 ± 5% were determined based on (134)Cs and (137)Cs, respectively. Annual, effective dose estimates from ingestion of (137)Cs and (134)Cs (1.8-3.7 μSv), arising from the consumption of tea beverages prepared from the most contaminated of these samples, are insignificant relative to both total (∼ 2.4 mSv) and ingested (∼ 0.28 mSv) annual effective doses received from naturally occurring radioactive sources. As such, there is no health concern arising from the consumption of green tea beverages contaminated with radiocesium at the levels encountered in this study.

Determination of heavy metals in the soils of tea plantations and in fresh and processed tea leaves: an evaluation of six digestion methods

Background

The aim of this study was to determine the levels of cadmium (Cd), chromium (Cr), lead (Pb), arsenic (As) and selenium (Se) in (1) fresh tea leaves, (2) processed (black) tea leaves and (3) soils from tea plantations originating from Bangladesh.

Methods

Graphite furnace atomic absorption spectrometry (GF-AAS) was used to evaluate six digestion methods, (1) nitric acid, (2) nitric acid overnight, (3) nitric acid–hydrogen peroxide, (4) nitric–perchloric acid, (5) sulfuric acid, and (6) dry ashing, to determine the most suitable digestion method for the determination of heavy metals in the samples.

Results

The concentration ranges of Cd, Pb, As and Se in fresh tea leaves were from 0.03–0.13, 0.19–2.06 and 0.47–1.31 µg/g, respectively while processed tea contained heavy metals at different concentrations: Cd (0.04–0.16 µg/g), Cr (0.45–10.73 µg/g), Pb (0.07–1.03 µg/g), As (0.89–1.90 µg/g) and Se (0.21–10.79 µg/g). Moreover, the soil samples of tea plantations also showed a wide range of concentrations: Cd (0.11–0.45 µg/g), Pb (2.80–66.54 µg/g), As (0.78–4.49 µg/g), and Se content (0.03–0.99 µg/g). Method no. 2 provided sufficient time to digest the tea matrix and was the most efficient method for recovering Cd, Cr, Pb, As and Se. Methods 1 and 3 were also acceptable and can be relatively inexpensive, easy and fast. The heavy metal transfer factors in the investigated soil/tea samples decreased as follows: Cd > As > Se > Pb.

Conclusion

Overall, the present study gives current insights into the heavy metal levels both in soils and teas commonly consumed in Bangladesh.

Earliest tea as evidence for one branch of the Silk Road across the Tibetan Plateau

Phytoliths and biomolecular components extracted from ancient plant remains from Chang'an (Xi'an, the city where the Silk Road begins) and Ngari (Ali) in western Tibet, China, show that the tea was grown 2100 years ago to cater for the drinking habits of the Western Han Dynasty (207BCE-9CE), and then carried toward central Asia by ca.200CE, several hundred years earlier than previously recorded. The earliest physical evidence of tea from both the Chang'an and Ngari regions suggests that a branch of the Silk Road across the Tibetan Plateau, was established by the second to third century CE.

Differentiation of black, green, herbal and fruit bagged teas based on multi-element analysis using inductively-coupled plasma atomic emission spectrometry

In the present paper, multi-element characterisation of 26 bagged teas was carried out using inductively-coupled plasma atomic emission spectrometry. Na, K, Ca and Mg were the metals with major contents. Among the essential elements, Fe and Zn were the most abundant, followed by Se, Cu, Mo and Cr. The tea bag samples also contained significant contents of Mn and Al. The chemometric techniques of linear correlation analysis, principal component analysis (PCA) and cluster analysis (CA) were used for differentiation of the tea bag samples according to their metal content. The samples analysed were classified into four groups by PCA and CA. The first group includes hibiscus, nettle, mint, rtanj tea, thyme, bearberry and sage. Green and black teas are in the second group. The third group contains strawberry, lime, pineapple, pomegranate, elder, blueberry, milfoil, apricot and chamomile. Exotic fruits, sweet cherry, forest fruits, apple, St John’s wort, rose hips, cherry and raspberry are in the fourth group.