Analysis of Naturally Occurring Fluoride in Commercial Teas and Estimation of Its Daily Intake through Tea Consumption

The aim of this study was to determine the levels of fluoride in commercial teas and to estimate the contribution of tea consumption to the fluoride recommended daily allowance. A total of 558 tea products in 6 categories, green tea, black tea, oolong tea, pu'er tea, white tea, and reprocessed tea, were collected in the period from 2010 to 2013. The levels of fluoride in infusions of these teas were determined by a fluoride‐ion selective electrode. The mean fluoride level in all of the tea samples was 85.16 mg/kg. For each category of tea, the mean fluoride levels were 63.04, 99.74, 52.19, 101.67, 159.78, and 110.54 mg/kg for green tea, black tea, white tea, pu'er tea, oolong tea, and reprocessed tea, respectively. The fluoride content of tea from 4 tea zones in descending order were Southern tea zone (111.39 mg/kg) > Southwest tea zone (78.78 mg/kg) > Jiangnan tea zone (71.73 mg/kg) > Jiangbei tea zone (64.63 mg/kg). These areas produced teas with lower fluoride levels than available foreign‐produced tea (161.11 mg/kg). The mean chronic daily intake (CDI) was 0.02 mg/(kg?day) or 1.27 mg/kg. Generally, consuming tea from these 6 categories does not result in the intake of excessive amounts of fluoride for the general population.     

Antioxidant and antimicrobial activities of tea infusions

Tea polyphenols, especially the catechins, are potent antimicrobial and antioxidant agents, with positive effects on human health. White tea is one of the less studied teas but the flavour is more accepted than that of green tea in Europe. The concentrations of various catechins in 13 different kinds of infusion were determined by capillary electrophoresis. The total polyphenol content (Folin–Ciocalteu method), the trolox equivalent antioxidant capacity (TEAC value determined with the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation) and the inhibitory effects of infusions on the growth of some microorganisms were determined. Five different infusions (black, white, green and red teas and rooibos infusion) were added to a model food system, comprising a sunflower oil-in-water emulsion containing 0% or 0.2% bovine serum albumin (BSA), and the oxidative stability was studied during storage at 37 °C. Oxidation of the oil was monitored by determination of the peroxide value.     

Monitoring and risk assessment of pesticide residues in yuza fruits (Citrus junos Sieb. ex Tanaka) and yuza tea samples produced in Korea

The objective of this study was to establish an analytical method to measure pesticides used to cultivate yuza (Citrus junos Sieb. ex Tanaka) and to analyze pesticide residue levels of yuza and yuza tea samples. Risk assessments were also performed by calculating estimated daily intake (EDI) and acceptable daily intake (ADI). An excellent linear correlation was achieved with coefficient correlation values of 0.9750–0.9999. Percent recoveries were 80.4–109.9% for most pesticides with a <6.9% relative standard deviation (RSD). The limits of quantification for the method were 0.10–0.67 μg/ml. The RSD of intra-day and inter-day variability was <15.3%. Seven pesticides in yuza (n = 80) and yuza tea (n = 75) were analyzed with the optimized analytical method. Acequinocyl, spirodiclofen and carbendazim were detected in yuza samples in the concentration range of 0.07–0.15 μg/g, 0.11–1.89 μg/g, and 0.03–5.15 μg /g, respectively, whereas chlorpyrifos, prothiofos, phosalone, and deltamethrin were not detected in yuza or yuza tea. The concentrations of acequinocyl, spirodiclofen and carbendazim ranged from 0.18–1.05 μg/g, 0.13–0.29 μg/g, and 0.17–2.36 μg/g, respectively, in yuza tea samples. The percent ratios of EDI to ADI for acequinocyl, spirodiclofen, and carbendazim were 24.6%, 22.7%, and 58.5%, respectively.     

Daily dietary intake of fluoride by Slovenian Military based on analysis of total fluorine in total diet samples using fluoride ion selective electrode

The purpose of this study was to develop an analytical procedure for determination of the amount of total fluoride in total diet samples, including drinking water and beverages. Samples were taken by the duplicate portion technique and decomposed by alkali carbonate fusion using KNaCO₃, and the amount of fluoride in solution was determined by fluoride ion selective electrode using the multiple known addition technique. The mean amount of total fluoride determined in 20 total diet samples obtained from the Slovenian Military was 1.84 ± 0.70 mg/kg on a dry matter basis. Accordingly the estimated daily intake was 1.50 ± 0.56 mg.     

Lithium content of some teas and their infusions consumed in China

Interest into the benefits of lithium (Li) has raised the issue that there are few data available on amounts of Li contained in different types of teas. Li concentrations of 30 teas and their infusions consumed in China were determined by inductively coupled plasma mass spectroscopy (ICP-MS). The highest Li content was found in Luobuma (Apocynum venetum) tea (>11 ppm). Li contents of other types of teas ranged from 0.02 to 0.6 ppm. According to our data and calculations, a daily consumption of 10 g Luobuma tea can give >85 μg Li intake. This is more than 85% of the minimum human adult Li requirement. However, other types of teas (10 g/day) can only provide <3% of the minimum Li requirement.     

Tea fluoride concentration and the pediatric patient

The purpose of this study was to measure the fluoride concentrations of various commercially available tea infusions, with a specific focus on risk of fluorosis. 100 ml infusions of 43 different tea brands were kept at a constant temperature of 85 °C and measured for fluoride concentration at 5, 15, 30, 60, and 120 min using a fluoride ion-specific electrode and millivolt meter. After 5 min at 85 °C mean fluoride concentration, in μg/ml with standard deviation, was 2.08 ± 1.24 for caffeinated tea infusions, 4.38 ± 0.97 for decaffeinated tea infusions, and 0.05 ± 0.02 for herbal teas. Caffeinated teas derived from the traditional source, Camellia sinensis, demonstrated significantly higher concentrations of fluoride than herbal teas (p < 0.01). Furthermore, decaffeinated teas demonstrated significantly higher concentrations of fluoride than caffeinated teas (p < 0.01). Some tea infusions may place a pediatric patient at higher risk for fluorosis if consumed as the primary source of hydration.     

Content of essential oil, terpenoids and polyphenols in commercial chamomile (Chamomilla recutita L. Rauschert) teas from different countries

Commercial samples of German chamomile (Chamomilla recutita (L.) Rauschert) tea (n = 13), packaged in different countries and purchased in Estonia either at food markets (9) or at retail pharmacies (4), were analysed for the essential oil and terpenoid content and constituents by GC-MS. Also the tea infusions were analysed for polyphenols spectrophotometrically and chromatographically by LC-DAD-MS/MS. The oils were obtained from chamomile flowers with yields of 0.10 - 0.61%. The existence of two types of chamomile tea, one rich in bisabolol oxides and the other in (−)-α-bisabolol, was established. The total content of polyphenols in gallic acid equivalents, estimated by the classical Folin-Ciocalteu method (TP_FC), was almost independent of the sample origin, but the total content of polyphenols (in chlorogenic acid equivalents) calculated on the basis of net areas under the chromatographic curves (AUC) of the infusions at 280 nm (TP_AUC) showed a significant variability as well as content of total flavonols (0.29-1.21%) or total phenolic acids (7.7-91.4 mg/200 ml). The major phenolic compounds in the chamomile infusions were chlorogenic acids, ferulic acid glycosides, dicaffeoyl quinic acids and apigenin glycosides. Based on the amounts of essential oil, terpenoids, total flavonols and major phenolic compounds, the quality of the commercial chamomile teas was very variable, and the chamomile teas available in pharmacies should be preferred for the medical purposes.     

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.     

Human exposure assessment of fluoride from tea (Camellia sinensis L.): A UK based issue?

Fluoride concentrations in UK tea, including the leading supermarket economy labelled products, were determined. Fluoride ranged from 93 to 820 mg/kg in the products and 0.43 to 8.85 mg/L in the infusions. The UK supermarket economy teas contained elevated fluoride, ranging from 3.60 to 7.96 mg/L in a 2 minute brewing infusion, comparable to Chinese brick tea, indicating the use of mature leaves in their manufacture. Considering the dietary reference intake (DRI) of 4 mg/day of fluoride for an adult consuming 1 L of tea, prepared from an economy tea, containing 6.0 mg/L fluoride, 75–120% of the DRI fluoride is available for absorption by the human system in the presence of food, increasing to 150% when fasting. Excess fluoride in the diet can lead to detrimental health effects such as fluorosis of the teeth and skeletal fluorosis and consuming economy branded tea will lead to exposure.     

Electrochemical determination of antioxidant capacity of fruit tea infusions

Cyclic voltammograms (CV) taken to 800 mV at a scan rate 100 mV s⁻¹ were used to quantify electrochemical properties of antioxidants present in 10 fruit tea infusions as well as to deduce antioxidant capacity from the Q₆₀₀ parameter (charge passed to 600 mV). A pronounced anodic current peak observed at 440 mV in all analysed fruit teas indicated that ortho-dihydroxy-phenol and gallate groups are the major contributors to the antioxidant capacity of investigated teas. Antioxidant composite index (ACI) was determined for each tea employing antioxidant capacity values from previous spectrophotometric determinations as well as the Q₆₀₀ parameter derived from CV. A ranking of the most potent teas was obtained: the fruit tea containing a large portion of rose hip fruit exhibited the highest ACI and a CV with the most pronounced anodic current peak at 440 mV pointing to the presence of ortho-dihydroxy-phenol and gallate group containing compounds. Strong positive correlation was established between antioxidant capacities deduced from CVs with those previously determined using established spectrophotometric techniques (FRAP, ABTS and DPPH assays).     

Determination of catechins in green tea infusions by reduced flow micellar electrokinetic chromatography

A sulfated-β-cyclodextrin (s-β-CD) modified reduced flow micellar electrokinetic chromatography (RF-MEKC) method was developed and validated for the determination of catechins in green tea. The optimal electrolyte consisted of 0.2% triethylamine, 50 mmol/L SDS and 0.8% s-β-CD (pH = 2.9), allowing baseline separation of five catechins in 4 min. The samples and standards were injected at 0.6 psi for 5 s under constant voltage of −30 kV. Sample preparation simply involved extraction of 2 g of tea with 200 mL water at 95 °C under constant stirring for 5 min. The method demonstrated excellent performance, with limits of detection (LOD) and quantification (LOQ) of 0.02–0.1 and 0.1–0.5 μg/mL, respectively, and recovery percentages of 94–101%. The method was applied to six samples of Brazilian green tea infusions. Epigallocatechin gallate (23.4–112.4 μg/mL) was the major component, followed by epigallocatechin (18.4–78.9 μg/mL), epicatechin gallate (5.6–29.6 μg/mL), epicatechin (4.6–14.5 μg/mL) and catechin (3.2–8.2 μg/mL).     

Cocoa tea (Camellia ptilophylla Chang), a natural decaffeinated species of tea – Recommendations on the proper way of preparation for consumption

Cocoa tea is a new natural decaffeinated tea. Three types of cocoa tea (green, oolong and black) were produced and their sensory evaluation scores accessed. Main components and their dissolution rates in ten infusions of the three teas were analyzed by HPLC and spectrophotometry. The comprehensive score of sensory evaluations was 85.1, 86.8 and 94.4, respectively. Upon fermentation the contents of water extract (46.67%, 41.8% and 40%), tea polyphenols (38.58%, 30.41% and 23.6%) and total catechins (23.51%, 17.68% and 4.02%) in green, oolong and black teas decreased gradually, and theaflavins (0.11%, 0.11% and 0.17%), thearubigins (4.29%, 5.00% and 9.71%), theabrownins (2.75%, 4.90% and 13.52%), water-soluble carbohydrates, flavonoid glycoside and gallic acid in the three teas increased gradually. Theobromine (3.52%, 3.43% and 3.71%) was the alkaloid present in cocoa tea and its content did not change upon fermentation. In the three teas, 9–25% of the main components dissolved in the first 10 s-infusion, more than 80% of most components dissolved in five infusions. A recommendation for consuming cocoa tea is to infuse tea leaves (g) with 50 times boiling water (ml) for 3 min, the first infusion should not be discarded and five infusions were sufficient.     

Determination of essential mineral concentrations in some turkish teas and the effect of lemon addition

Essential elemental concentrations of Turkish black, green, and earl grey tea infusions were determined with and without added lemon. Daily percentage elemental intake values from these 3 teas with and without lemon addition were calculated based on Recommended Dietary Allowances (RDA). Calcium (Ca), cobalt (Co), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), sodium (Na), selenium (Se), and zinc (Zn) concentrations were increased after lemon addition. The chromium (Cr) concentration was decreased in green and earl grey teas and increased in black tea after lemon addition. The manganese (Mn) concentration was increased in green tea and decreased in black and earl grey teas after lemon addition. The phosphorus (P) concentration was increased in earl grey and green teas, and decreased in black tea after lemon addition. The daily intake value of Mn was found above the RDA value.     

The composition of polyphenols and methylxanthines in teas and herbal infusions

The popularity of tea is increasing on the global aspect because of its role as a significant source of phenolic compounds in human diet. The purpose of this study was to determine and compare the phenolic and methylxanthine composition as well as the antioxidant capacity of white, green, Oolong and black teas, and chamomile and linden infusions depending on the extraction conditions (water temperature and multiple extractions). The content of total phenols and total flavonoids in teas and herbal infusions was determined by using UV/vis spectrophotometric methods, whilst individual polyphenols (phenolic acids and flavan-3-ols) and methylxanthines were identified and quantified by using high performance liquid chromatography coupled with photodiode array detection. In order to determine the antioxidant capacity of teas the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging assays were applied. The highest content of phenolic compounds was determined in green tea, which also demonstrated the highest antioxidant capacity, whilst herbal infusions were characterised with the lowest content of phenolic compounds, as well as the lowest antioxidant capacity. The highest content of caffeine, as the most abundant methylxanthine, was determined in black tea. Extraction at 100 °C is the most effective to extract the highest content of polyphenols and methylxanthines in all studied teas.     

Unfermented and fermented rooibos teas (Aspalathus linearis) increase plasma total antioxidant capacity in healthy humans

The aim of the study was to assess the effect of drinking rooibos tea (Aspalathus linearis) on total antioxidant capacity (TAC), lipid triacylglycerols, cholesterol and glycaemia plasma levels in humans. In vitro, unfermented rooibos tea displayed a 28% higher value of TRAP than did the fermented beverage. An acute intervention study, cross-over design, was performed, with 15 healthy volunteers who consumed 500 ml of either water, unfermented or fermented rooibos teas. Plasma antioxidant capacity increased significantly with both teas, reaching a peak at 1 h post-consumption (+6.6%, p < 0.05 fermented tea; +2.9%, p < 0.01 unfermented tea). No changes in triacylglycerols, cholesterol or uric acid were observed with any of the treatments. A transitory increase in glycaemia at 30 min was linked to glucose upload. The data show that rooibos teas represent a source of dietary antioxidants in humans.     

Screening of 70 medicinal plant extracts for antioxidant capacity and total phenols

The total phenolic content and related total antioxidant capacity of 70 medicinal plant infusions was analyzed. Infusions were prepared in common way in which teas are prepared for human consumption. The total phenolics were measured by Folin–Ciocalteau assay. The total antioxidant capacity was estimated by Ferric Reducing/Antioxidant Power (FRAP) assay. To make practical comparison of relative antioxidant potential of phenolics extracted from selected medicinal plants, the phenol antioxidant coefficient (PAC) was calculated for each infusion. The total phenolic content of medicinal plant infusions ranges from 9 to 2218 mg/L. The FRAP range from 0.06 to 25 mM/L. There was significant linear correlation between total phenolic content and FRAP. According to their antioxidant capacity, 70 medicinal plant extracts can be divided in five groups: (a) very low FRAP (<1 mM/L) n = 9; (b) low FRAP (1–5 mM/L), n = 37; (c) good FRAP (5–10 mM/L), n = 15; (d) high FRAP (10–20 mM/L), n = 8; and (e) very high FRAP (>20 mM/L), n = 1 medicinal plant extract. The PAC was ranging from 1.1 to 3.9 (average 2.4). The best results were obtained for Melissae folium infusions: high phenolic concentration, very high FRAP (>20 mM/L) and PAC > 3. The effect of infusion time and infusion temperature on the phenolic content, FRAP, and free radical scavenging ability was tested. DPPH radical scavenging ability of Melissae folium phenolics was similar to (+)-catechin but not as good as for quercetin. Compared to Trolox and vitamin C, Melissae folium phenolics were more efficient free ABTS radical scavengers. The results indicate that Melissae folium infusions could be an important dietary source of phenolic compounds with high antioxidant capacity comparable with red wine or beverages like tea.     

Total and acid-soluble fluoride content of infant cereals, beverages and biscuits from Brazil

Total fluoride (TF) and HCl 0.01 M ('gastric juice')-soluble fluoride (SF) were analysed in infant foods, beverages and calcium-rich biscuits. Samples were divided into seven categories: children cereals (A), chocolate-flavoured milk (B), soy beverages (C), filled biscuits (D), non-filled biscuits (E), wafer biscuits (F) and corn starch biscuits (G). Mean TF concentrations ± SD (amplitude, unit µg F ml^-1 or µg F g^-1) were: (A) 4.25 ± 3.04 (0.20 - 7.84, n = 6); (B) 0.34 ± 0.47 (0.05-1.27, n = 6); (C) 0.15 ± 0.07 (0.09-0.29, n = 8); (D) 8.44 ± 1.76 (7.65-10.47, n = 4); (E) 12.41 ± 1.15 (10.69-13.68, n = 4); (F) 0.35 ± 0 (0.34-0.36, n = 4) and (G) 7.77 ± 1.12 (6.86-8.68, n = 2). Five samples of cereals, one sample of chocolate-flavoured milk and 10 samples of biscuits were analysed for SF. In cereals analysed for SF, all fluoride was soluble, while for the chocolate-flavoured milk, approximately 50% of TF was soluble. Regarding the biscuits analysed for SF approximately 20% of TF was soluble. It was observed that some of the cereals and beverages, and most of the biscuits analysed, might be important contributors to total daily fluoride intake. When consumed just once per day, cereals and beverages might supply up to 25% of the maximum recommended daily fluoride intake (0.07 mg F kg^-1 body weight) for a 2-year-old child (12 kg). For the filled, non-filled and corn starch biscuits, when 3, 32 or 20 units of them, respectively, are consumed just once per day, they may supply up to 16% of the maximum recommended daily fluoride intake. However, only approximately 25% of fluoride absorption occurs from the stomach and 75% from the small intestine. Therefore, a higher fluoride bioavailability is possible.     

Aluminium and fluoride in hospital daily diets and in teas

The levels of aluminium and fluoride have been determined in hospital daily diets including breakfast, dinner and supper, as well as in black teas and herbal teas purchased from the local market. In tea, aluminium was determined directly in a sample solution by atomic absorption spectroscopy using nitrous oxide and an acetylene flame. For analysis of the hospital diet, samples containing lower levels of aluminium were analysed using a spectrophotometric method which measured aluminium in the form of a 8-hydroxyquinoline complex. Decomposition of the samples was achieved using a mixture of concentrated acids [nitric (HNO₃), perchloric (HClO₄) and sulphuric (H₂SO₄)] in platinum dishes. Fluoride was assayed by spectrophotometry using a microdiffusion procedure with a mixture of concentrated HClO₄ and silver sulphate, trace amounts of the released fluoride [as hydrogen fluoride (HF)] were trapped on the alkaline surface of a Petri dish and then determined in the form of an alizarin-fluoride complex. The mean level of aluminium found in hospital daily diets amounted to 21.3±12.3 mg and the mean level of fluoride was 1.38±1.12 mg per adult person. In the 16 samples of commercially available brands of black teas, the levels of aluminium and fluroide ranged from 445 to 1552 ppm (mean=897±264 ppm) and from 30 to 340 ppm (mean 141±85 ppm), respectively. In six herbal teas, the mean levels of aluminium and fluoride were lower, and amounted to 218.9±150.7 ppm and 6.0±6.9 ppm, respectively. This study has shown that concern about a high intake of aluminium and fluoride from these foods is unfounded.     

Determination of anionic minerals in black and kombucha tea using ion chromatography

A simple, rapid and accurate method for the determination of anionic minerals in tea brew has been developed. The quantitative determination of anions – fluoride, chloride, bromide, iodide, nitrate, phosphate and sulphate was accomplished by anion exchange chromatography with conductometric detection. A Metrosep Anion Dual 2 analytical column connected in series with a Metrosep RP guard column was used for anion separation. A solution containing a mixture of 1.3 mM Na₂CO₃ and 2 mM NaHCO₃ was used as eluent. The method requires a simple sample clean-up procedure to remove the interfering organic components from the tea brew. The limit of detection for different anionic minerals were in the range 0.01–0.05 μg mL⁻¹ and the relative standard deviation were in the range 4–6% for the overall method. The recovery of different anionic minerals added was in the range 95–106%. The method was applied to the determination of anions in black and kombucha tea.     

Effect of green and black teas (Camellia sinensis L.) on the characteristic microflora of yogurt during fermentation and refrigerated storage

The effect of tea on the fermentation and survival of yogurt microorganisms was studied. Green and black teas were added to milk at the beginning of fermentation. Acidity of yogurt products and survival of their microflora were studied during 42 days at 4 °C. Results showed that the presence of tea did not significantly (P < 0.05) influence the yogurt characteristic microorganisms. HPLC studies demonstrated that yogurt bacteria did not affect tea catechins when they were incubated together for 48 h. Indeed, all five products reached about 10⁹ CFU/ml after 6 h of fermentation. Viability during 6 weeks storage at 4 °C varied very little (8.35 < log CFU/ml < 8.65). Similarly, green and black teas had no effect on lactic acid levels of the final products (after 6 weeks of storage, acidity remained above 80 °D). According to these findings, addition of teas or tea catechins to yogurt can be recommended to take advantage of their beneficial properties on human health attributed to their antioxidant and antimicrobial activities.