Fluoride in tea from Shandong Province,China and exposure assessment

ABSTRACT

In this study fluoride in 170 tea samples from Shandong province (China) was determined using a selective ion electrode. The fluoride concentrations ranged from 31.2 to 338 mg/kg with an average of 119 mg/kg. The mean fluoride concentrations were 164, 121, 98.7 and 96.8 mg/kg, which corresponded to Pu’erh tea, green tea, oolong tea and black tea, respectively. Moreover, 4.7% of the analysed samples exceed the legal limit of 200 mg/kg recommended by China. The estimated daily intake of fluoride via drinking tea for an adult was between 0.655 and 1.07 mg/person/day, which were lower than the provisional maximum tolerable daily intake value of 3.5 mg/person/day set by the National Health and Family Planning Commission of the People’s Republic of China. In future, maintaining a surveillance programme to monitor the trend of fluoride in tea is necessary for food safety and human health.     

Fluoride in teas of different types and forms and the exposure of humans to fluoride with tea and diet

Human exposure to the fluoride (F) from commercial teas was assessed. The efficacy of the F leaching was determined from the total F (F_t) contents in the teas (53–435 mg/kg) and the F concentrations in tea infusions (0.31–3.55 mg/l of free F available to human organism). Both were determined with a fluoride ion selective electrode. The efficacies of F leaching from the green, oolong and black teas were 55–90% with continuous, and 74–100% by repeated infusions, and were not affected by the type or the manufactured form. Lower efficacies were observed from Pu’erh teas, 21–38% with continuous, and 37–59% by repeated infusions. The daily intake of F with daily consumption of five cups of tea can represent 9–101% of the adequate intake (AI) for an adult person with 70 kg, and with tea and diet 25–173% of the AI in non-fluoridated and 35–210% of AI in fluoridated areas. The upper limits of these intakes can be already associated with a risk of developing F-related adverse effects.     

红茶、绿茶、乌龙茶活性成分抗氧化性研究

目的与方法：通过醇提得到各种茶多酚提取液,酒石酸亚铁法测定了多酚的含量;水提得到各种茶多糖提取液,用硫酸- 苯酚法测定其中多糖的含量。通过DPPH·法、水杨酸法及邻苯三酚法测定不同茶叶中多酚、多糖含量对自由基的清除作用的影响,对比研究八种茶叶的抗氧化能力。结果：不同茶叶中多糖的含量从2.19%增大到2.89% (半发酵乌龙茶＞红茶＞绿茶),抗氧化能力：红茶＞绿茶＞乌龙茶(DPPH·法);红茶＞绿茶＞乌龙茶(水杨酸法);红茶＞乌龙茶＞绿茶(邻苯三酚法);不同茶叶中多酚的含量从1.71% 增大到9.75% (绿茶＞半发酵乌龙茶＞红茶);结论：茶多糖和多酚是茶叶的主要抗氧化成分。绿茶的抗氧化作用主要来自茶多酚,红茶的抗氧化作用主要来自茶多糖。除乌龙茶多糖提取液外,两种抗氧化成分的抗氧化能力与其含量成量效关系。     

Effect of consecutive steeping on antioxidant potential of green,oolong and black tea

After water, tea is considered to be one of the most consumed drinks worldwide. To get the maximum benefit from the whole‐leaf teas, the manufacturers provide instruction that these teas can be steeped 2–3 times over 6–8 h. In this study, the effect of consecutive steeping on radical‐scavenging ability of whole leaf green tea (unfermented), oolong tea (partially fermented) and black tea (fully fermented) was determined. Green tea showed the highest level of antioxidant activity, total phenolic and flavonoid content followed by oolong tea and black tea irrespective of the number of steeping done. The result also demonstrated that re‐steeping reduced the antioxidant potential of teas. Moreover, it was revealed that green tea is the best candidate for re‐steeping followed by oolong and then black tea.     

广东本地产茶叶矿物质元素与茶多酚含量调查分析

目的 调查广东省当地种植的茶叶矿物质元素和茶多酚含量范围、成分差异及分布特征.方法 采集2017-2018年广东省7个茶叶产区具有代表性的茶叶(绿茶、乌龙茶、红茶)样品,按照国标法对样品中的9种矿物质元素和茶多酚的含量进行测定,对比分析不同种类、不同产区中矿物质元素和茶多酚的含量差异.结果 乌龙茶中钾元素的平均含量为1...     

Safety evaluation on fluoride content in black tea

Fluoride content in black tea in various commodities, packages, and preparation processess was assayed and its safety evaluated. A fluoride ion selective electrode method was used to determine the fluoride content in 20 tea samples, in various black tea commodities, namely stick-shaped, granular, and canned or bottled tea beverage, originally produced in India, Sri Lanka, China, Japan and UK, and milk–tea after addition of milk and sugar. The fluoride content of 5 stick-shaped black teas was 96.9–148 mg/kg, that of 8 granular black tea was 139–223 mg/kg, and that of 3 canned or bottled beverage black tea beverages was 0.70–0.96 mg/l, respectively. Neither the bagged black tea paper nor the addition of milk and sugar affected the ionic fluoride level within the tea. These results suggest that, for heavy black tea drinkers, the fluoride intake in areas with drinking water fluoridation, and also other probable sources of fluoride, may approach or reach the level of risk from chronic fluoride intoxication.     

Discrimination of teas based on total luminescence spectroscopy and pattern recognition

This paper reports on the application of total luminescence spectroscopy to discriminate between seven different types of tea: four bottled liquid Japanese teas (oolong, green, houji and black teas) and three leaf teas (Kenya, Assam and Ceylon teas). Total luminescence spectra were recorded by measuring the emission spectra in the range 300–700 nm at excitation wavelengths from 250 to 590 nm. Discrimination of teas based on their spectral data was performed by principal component analysis, a common chemometric method used for data reduction and visualisation. The results demonstrate the ability of fluorescence techniques to differentiate between green tea (unfermented), black tea (fermented) and oolong tea (partially fermented). Copyright © 2006 Society of Chemical Industry     

高效液相色谱-二极管阵列法检测四川绿茶、黄茶、黑茶、红茶和青茶中甲基化儿茶素含量

采用高效液相色谱-二极管阵列检测法(HPLC-DAD)对四川省雅安、成都、乐山、宜宾、绵阳23家企业生产的绿茶、黄茶、黑茶、红茶和青茶中48个茶样的(-)-表没食子儿茶素-3-O(3-O-甲基)没食子酸酯(EGCG3″Me)含量进行了比较研究。结果表明:青茶EGCG3″Me含量最高,在3.14~6.08 mg/g之间,平均值为4.40 mg/g;黑茶EGCG3″Me含量在0~1.72 mg/g,平均值为0.35 mg/g;绿茶和黄茶中EGCG3″Me含量较低;绿茶中含量在0~0.39 mg/g之间,平均值为0.10 mg/g;黄茶中含量在0~0.09 mg/g之间,平均值为0.05 mg/g;红茶中未检出。各茶类间EGCG3″Me含量差异显著,主要原因在于加工所用鲜叶原料(品种、采摘标准等)及加工工艺等不同。建议易过敏人群应适当饮用青茶。     

Distribution of Catechins, Theaflavins, Caffeine, and Theobromine in 77 Teas Consumed in the United States

ABSTRACT: To help define the composition of commercial teas consumed in the United States, we have developed and validated an high-performance liquid chromatography (HPLC) method to analyze levels of catechins, theaflavins, and alkaloids in 77 commercial black, green, specialty (brown rice, white, oolong), and herbal teas extracted with hot water to simulate home use. The following 13 compounds were separated in a single analysis on an Inertsil ODS-3v column with acetonitrile/potassium dihydrogen phosphate as the mobile phase: (−)-epigallocatechin, (+)-catechin, (−)-epicatechin, (−)-epigallocatechin-3-gallate, (−)-gallocatechin-3-gallate, (−)-epicatechin-3-gallate, (−)-catechin-3-gallate, theaflavin, theaflavin-3-gallate, theaflavin-3'-gallate, theaflavin-3, 3'-digallate, caffeine, and theobromine. The data show that (1) extraction time from 3 min to 20 min did not significantly affect measured levels of tea compounds and (2) there was a wide variation in the composition of the tea compounds both within each tea category and among categories: black teas contained both theaflavins and catechins, green and white teas contained catechins and trace amounts of theaflavins, herbal teas contained very low amounts of all tea compounds. A statistical profile of the distribution of catechins, theaflavins, caffeine, and theobromine in the evaluated teas offers consumers a choice of teas containing high levels of health-promoting compounds.     

Pu-erh tea, green tea, and black tea suppresses hyperlipidemia, hyperleptinemia and fatty acid synthase through activating AMPK in rats fed a high-fructose diet

Although green tea extract has been reported to suppress hyperlipidemia, it is unclear how tea extracts prepared from green, oolong, black and pu-erh teas modulate fatty acid synthase expression in rats fed on a high-fructose diet. In this animal study, we evaluated the hypolipidemic and hypoleptinemia effect of these four different tea leaves fed to male Wistar rats for 12 weeks. The results showed that a fructose-rich diet significantly elevated serum triacylglycerols, cholesterol, insulin, and leptin concentrations, as compared with those in the control group. Interestingly, consuming tea leaves for 12 weeks almost normalized the serum triacylglycerols concentrations. Again, rats fed with fructose/green tea and fructose/pu-erh tea showed the greatest reduction in serum TG, cholesterol, insulin and leptin levels. In contrast, serum cholesterol and insulin concentrations of the fructose/oolong tea-fed rats did not normalize. The relative epididymal adipose tissue weight was lower in all rats supplemented with tea leaves than those fed with fructose alone. There was molecular evidence of improved lipid homeostasis according to fatty acid synthase (FAS) protein expression. Furthermore, supplementation of green, black, and pu-erh tea leaves significantly decreased hepatic FAS mRNA and protein levels, and increased AMPK phosphorylation, compared with those of rats fed with fructose only. These findings suggest that the intake of green, black, and pu-erh tea leaves ameliorated the fructose-induced hyperlipidemia and hyperleptinemia state in part through the suppression of FAS protein levels and increased AMPK phosphorylation.     

表面增强拉曼光谱法快速检测茶叶中百草枯与敌百虫农药残留

目的 对茶叶中的百草枯与敌百虫进行定性与定量检测,满足茶叶生产中对这两种农药残留的快速、便携、准确的检测需求。方法 采用表面增强拉曼光谱(surface enhanced Raman spectroscopy SERS)技术对不同浓度的百草枯和敌百虫农药标准溶液进行光谱采集和峰位归属,再对不同茶类茶汤中的梯度农药残留进行检测,建立峰强与农药残留浓度的线性关系。结果 发现在不同茶类中,以茶叶中百草枯在843 cm_^-1处的拉曼特征峰作为识别峰所建立回归模型预测的百草枯在绿茶、红茶、黑茶茶汤中的最低可检测浓度为1×10_^-7 moL/L,在乌龙茶茶汤中的最低可检测浓度为1×10_^-6 moL/L,灵敏度均满足国家规定的茶叶中百草枯最大农药残留限量(0.2 mg/kg);敌百虫的检测中,茶汤中咖啡碱的SERS峰强受敌百虫浓度影响,随敌百虫浓度的增加而减小且呈现显著负线性相关,因此可用茶叶中咖啡碱的拉曼特征峰作为敌百虫浓度的间接识别的依据,所建立的回归模型显示敌百虫在绿茶、红茶、乌龙茶茶汤中的最低可检测浓度为1×10_^-7 moL/L;在黑茶茶汤中的最低可检测浓度为1×10_^-6 moL/L,均可达到国家茶叶最大残留限量(2 mg/kg)。结论 使用SERS技术可实现不同茶类茶汤中的百草枯与敌百虫农药残留的简单、快速、准确分析。     

Chemical Forms of Iron, Calcium, Magnesium and Zinc in Black, Oolong, Green and Instant Black Tea

The chemical forms of iron, calcium, magnesium and zinc were quantified in black, oolong, green and instant black tea infusions. Iron was least soluble in black tea (69%) and most soluble in instant black tea (100%). Calcium was least soluble in green tea (46%) and instant black tea (35%). Almost all magnesium and zinc (89%-98%) were soluble in all teas. The fermented teas had more complexed iron than unfermented tea. Conversely, more ionic iron was in green tea. All ionic iron in the four teas was in the ferric state. Tannase, a polyphenol degrading enzyme, and lemon juice solubilized iron and calcium in some teas. Tannase and lemon juice might reduce the detrimental effect of tea on mineral availability.     

Comparison of catechins and volatile compounds among different types of tea using high performance liquid chromatograph and gas chromatograph mass spectrometer

As tea is one of the most popular beverages consumed worldwide, it is important for customers and business investigators to develop an easy and reliable method to discriminate between different types of teas from each other. A total of eighty‐seven types of various white, green, oolong, black and Puer teas were collected from the major tea estates in China, and their catechin contents and volatile compounds were compared by high performance liquid chromatograph and gas chromatograph mass spectrometer. It was found green tea contained the highest concentrations of total catechins, (?)‐epicatechin gallate (ECG) and (?)‐epigallocatechin gallate (EGCG), while oolong teas contained the highest concentrations of (?)‐epigallocatechin (EGC) among these five types of teas. The aroma composition and their quantities in different types of teas varied quite widely. The concentration of ECG, EGCG, pentanal, hexanal, methyl jasmonate, indole, (E,E)‐2,4‐hexadienal and 1,2,3‐trimethoxybenzene was shown to be different and could be used to discriminate white, green, oolong, black and Puer teas. The result showed that different types of teas could be partially classified by cluster analysis using index of individual catechins and volatile components.     

Dynamic changes in flavonol glycosides during production of green,yellow, white,oolong and black teas from Camellia sinensis L. (cv. Fudingdabaicha)

Flavonol glycosides with low thresholds are important flavour substances in tea leaves. This study monitored the dynamic changes in flavonol glycosides during the production of different teas. The fresh leaves of cv. Fudingdabaicha with 15.77 mg g⁻¹ of total flavonol glycosides (TFG) were respectively processed into green, yellow, white, oolong and black teas. A reduction of TFG was observed for different teas, amongst which black tea contained the lowest level of TFG (9.83 mg g⁻¹), followed by oolong tea (11.96 mg g⁻¹), while green, yellow and white teas contained similar levels of TFG (~13.70 mg g⁻¹). Fixation was crucial to maintain the stability of flavonol glycosides due to its inactivation effect on enzymes at high temperature. Principal component analysis results indicated that flavonol glycosides were vulnerable to fermentation, and the stabilities of flavonol glycosides were related with aglycone and glycoside moiety.     

Inhibition of angiotensin converting enzyme (ACE) activity by polyphenols from tea (Camellia sinensis) and links to processing method

The focus of this study was to investigate Angiotensin Converting Enzyme (ACE) inhibiting activity across 34 teas (Camellia sinensis) produced by 5 different processing methods including green (GT), oolong (OT), white (WT), black (BT) and dark (DT) teas. In vitro ACE inhibitory activity was affected by the tea processing method with IC(50) values for ACE inhibition: green < oolong < white < black < dark teas. Substrate-dependence of the reaction kinetics was studied for GT and BT polyphenolic size fractions either < or > 3 kDa and also Green Tea Polyphenolic Isolate (GTPI), and revealed that enzyme velocity curves fitted allosteric, not Michaelis-Menten, relationships. Inhibition was weakly dependent on substrate concentration for GT fraction >3 kDa and independent of substrate concentration for all other GT and BT size fractions and GTPI. Furthermore, evidence for direct inactivation of ACE by GTPI was demonstrated. Overall, the results suggest that tea polyphenolics exert a mixed mode of in vitro inhibition of ACE, mostly of a kinetically uncompetitive type. The results are discussed in the context of in vivo and epidemiological evidence for regulation of blood pressure by tea consumption.     

Comparison of the relative dissipation rates of endosulfan pesticide residues between oolong and green tea

The dissipation behaviour of endosulfan in dry made-tea leaves of oolong and green tea was compared to establish whether there was any difference in dissipation rates between the two teas. The dissipation of endosulfan in oolong and green tea corresponded with a first-order kinetics curve. The average half-life of endosulfan (n = 12) was 1.60 ± 0.44 days in green tea and 2.01 ± 0.55 days in oolong tea, showing a statistically significant difference, and indicating that the dissipation of the pesticide was significantly slower in oolong tea than that in green tea. Although the initial levels of residual endosulfan were lower in oolong tea, due to the slower dissipation rate, the residues 5-7 days after application were higher in oolong than in green tea. It is suggested that the minimum interval between endosulfan application and tea leaf harvesting is 7 days for green tea and 10 days for oolong tea in the case where the maximum residue limit of endosulfan in made-tea is fixed as 10 mg kg^-1.     

Analysis of Trace Metals and Perfluorinated Compounds in 43 Representative Tea Products from South China

Six trace metals (Cd, Pb, Cr, Cu, Zn, and Mn) and 2 perfluorinated compounds (PFCs), perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), were analyzed in 43 representative tea products (including 18 green, 12 Oolong, and 13 black teas) from 7 main tea production provinces in China, using the atomic absorption spectrophotometer for trace metals analysis and HPLC‐MS/MS for PFOS and PFOA analysis. The average contents of the 3 essential metals Mn, Cu, and Zn ions in the tea samples were 629.74, 17.75, and 37.38 mg/kg, whereas 3 toxic metals Cd, Cr, and Pb were 0.65, 1.02, and 1.92 mg/kg, respectively. The contents of heavy metals in the 3 types of tea were in the order of black tea > Oolong tea > green tea. Both PFOS and PFOA contents were low and PFOA content was higher than PFOS in the tea samples. The highest concentration of PFOA was 0.25 ng/g dry weight found in a Hunan green tea. The Principal component analysis was performed with the trace metals and PFCs to analyze the relationships of these indices. The results showed that black teas had higher trace metals and PFCs than green and Oolong teas, and the teas from Hunan and Zhejiang provinces had higher Pb and Cr than others.     

Determination of catechins and flavonol glycosides in Chinese tea varieties

A standardised profiling method based on high performance liquid chromatography combined with ultraviolet (UV) and mass spectrometric detection (MS) was established to analyse the phenolic compounds of selected tea varieties used for manufacturing of green, black and oolong teas. The composition and content of 24 tea constituents were analysed, including catechins, flavonol and flavones glycosides, phenolic acids and purine alkaloids. Each tea variety had a unique chemical profile. The compositions of catechins were lower in the tea varieties for green tea manufacturing, while the content of myricetin glycosides was the lowest in the tea variety for oolong tea manufacturing. The content of individual phenolic compounds in the selected tea varieties is highly variable. However, the content of total catechins is proposed to be helpful to classify tea according to the future application as non fermented green and fermented oolong or black tea.     

Gastrointestinal Absorption of Aluminum from Teas in Rats

ABSTRACT: Gastrointestinal absorption of aluminum (Al) contained in black tea, green tea, and oolong tea compared with that of Al citrate was investigated using Wistar rats. The serum Al level in the rats administered orally with Al citrate increased by 7.9 times that of the basal level. In contrast, the administration of teas, at the equivalent dose of Al, increased only slightly the serum Al level (30 to 58%). Among 3 types of tea infusions, the serum Al level in the green tea group was relatively high compared to those in the black tea and oolong tea groups, although the difference was not significant. These results showed that the absorption rates of Al from ingestion of tea infusions were much lower than that of free form Al. It was also suggested that there were no marked differences in Al absorption rates from black tea, green tea, or oolong tea in the gastrointestinal tract.     

Rapid and selective quantification of L-theanine in ready-to-drink teas from Chinese market using SPE and UPLC-UV

An ultra performance liquid chromatography (UPLC) method combined with solid phase extraction (SPE) sample pre-treatment was developed and validated for the rapid quantification of L-theanine in ready-to-drink (RTD) teas. UPLC analysis of twenty-seven RTD teas from the Chinese market revealed that the L-theanine levels in various types of RTD teas were significantly different. RTD green teas were found to contain highest mean L-theanine level (37.85±20.54 mg/L), followed by jasmine teas (36.60±12.08 mg/L), Tieguanying teas (18.54±3.46 mg/L) black teas (16.89±6.56), Pu-erh teas (11.31±0.90 mg/L) and oolong teas (3.85±2.27 mg/L). The ratio of total polyphenols content to L-theanine content could be used as a featured parameter for differentiating RTD teas. L-theanine in RTD teas could be a reliable quality parameter that is complementary to total polyphenols.