Aluminium content in tea leaves and in differently prepared tea infusions

Aluminium content of tea leaves has been engaging the attention during recent years because of its uptake in the form of beverages such as tea. Hence, data were generated on the Al content in tea and its infusions, using an inductively coupled plasma spectrometer. The average values of Al in fresh tea leaves and commercial tea powders were 250 and 325 μg/g dry wt, respectively. Tea infusions contained 20–80 μg/g of Al. Al complexes with tea components like tannic acid and theoflavins were studied and stability characteristics as well as the nature of the complexes were computed.     

Total content and speciation of aluminium in tea leaves and tea infusions

A total of 29 tea samples of different origin, 13 green tea samples, 13 black tea samples, two semi-fermented and one white tea, imported to the Czech Republic, were collected and analysed for total content of aluminium (Al) in tea leaves and tea infusions, as well as for Al compounds in these infusions. The total content of metals in tea leaves differs according to the type of tea (green or black) and is probably influenced by many factors, e.g., soil properties. The HPLC/IC speciation of Al in tea infusions was performed for all samples. The addition of Al³⁺ to the tea infusion proved that Al³⁺, Al(Y)²⁺ and Al(X)¹⁺ species can be determined in tea infusions. Increased extraction time did not show any affect on Al speciation, neither did the addition of sugar. After the addition of lemon juice, the speciation changed in one sample of black tea and five samples of green tea. These findings suggest that lemon juice as an additive can significantly influence Al speciation in tea infusions.     

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.     

Comparison of anti-glycation capacities of several herbal infusions with that of green tea

Advanced glycation end-products (AGEs) are implicated in the pathogenesis of diabetic microvascular complications and microvascular complications of the aged. Dietary compounds that can reduce glycation may reasonably serve as valuable adjuvants, promoting the health of the aged and diabetics. This work evaluates and compares the anti-glycation activities of different herbal infusions with that of green tea, a well-documented anti-glycation beverage. The anti-glycation activity of herbal infusions were determined based on the ability of an infusion to attenuate the formation of fluorescent AGEs in glucose- and methylglyoxal-mediated protein glycation systems. All of the tested herbs except for lemongrass and rosemary—balm, mint, black tea, sage and common verbena—had potent anti-glycation abilities that exceeded or equalled that of green tea. Additionally, the amounts of phenolics and flavonoid in the herbal infusions were highly correlated with their anti-glycation activity, revealing that the anti-glycation activity of herbal infusions was primarily attributable to phenolics, particularly flavonoids.     

铬天青S分光光度法测定茶汤中的铝含量

采用浓缩-湿法消化对茶汤进行前处理,用分光光度法测定茶汤中的铝含量,建立了浓缩-湿法消解-铬天青S分光光度法测定茶汤中铝的方法。实验结果表明,本方法前处理简单易行,检测结果准确度、灵敏度高、精密度好,在0～6μg/25mL浓度范围内,呈良好的线性关系,相关系数r=0.9997,样品的加标回收率在96.7%～100%,RSD为1.84%,该法方便、简单、快速、准确、可靠,适合茶汤中铝的测定。     

Speciation of manganese in tea leaves and tea infusions

A speciation scheme was developed for identification of the chemical forms of manganese in tea leaves and tea infusions. The range of manganese in five different groups of tea leaves was found as 1107–2205 μg g⁻¹ on dry basis. It was noted that 30.0% of Mn was passed into the water that was present in the form of Mn(II), and also 2.5% of Mn was distributed in the total organic bound and was passed into the various solvents.     

Antioxidant capacity of herbal infusions and tea extracts: A comparison of ORAC-fluorescein and ORAC-pyrogallol red methodologies

Oxygen radical absorbance capacity (ORAC) values have been obtained for a series of teas and herbal infusions employing 2,2′-azo-bis(2-amidinopropane) as free radical source, and fluorescein and pyrogallol red as target molecules. The amounts of phenols in the extracts were evaluated by Folin’s methodology. ORAC values are extremely dependent upon the employed target molecule. Even more, relative ORAC values measured for different infusions depend upon the employed methodology. For example, ORAC-fluorescein value of Aloysia citriodora is larger than that of green tea, while if pyrogallol red is employed as target molecule green tea appears as nearly nine times more efficient. Similarly, for extracts with comparable amounts of phenols, herbal infusions are more efficient than teas by ORAC-fluorescein, while opposite conclusions are obtained if ORAC-pyrogallol red values are considered. Extreme care must then be taken for conclusions obtained from ORAC values estimated by employing a single target molecule.     

Residues and contaminants in tea and tea infusions: a review

Consumers are very aware of contaminants that could pose potential health hazards. Most people drink tea as an infusion (adding hot water); however, in some countries, including India, China and Egypt, tea is drunk as a decoction (tea and water are boiled together). An infusion usually brings the soluble ingredients into solution, whereas a decoction brings all soluble and non-soluble constituents together. Therefore, a cup of tea may contain various kinds of contaminants. This review focuses on green and black tea because they are most commonly consumed. The target was to examine the transfer rate of contaminants – pesticides, environmental pollutants, mycotoxins, microorganisms, toxic heavy metals, radioactive isotopes (radionuclides) and plant growth regulators – from tea to infusion/brewing, factors contributing to the transfer potential and contaminants degradation, and residues in or on the spent leaves. It is concluded that most contaminants leaching into tea infusion are not detected or are detected at a level lower than the regulatory limits. However, the traditional practice of over-boiling tea leaves should be discouraged as there may be a chance for more transfer of contaminants from the tea to the brew.     

Tracking residual organochlorine pesticides (OCPs) in green,herbal, and black tea leaves and infusions of commercially available tea products marketed in Poland

The content of residual organochlorine pesticides (OCPs) was examined in green, herbal, and black tea leaves as well as in their infusions prepared from tea products marketed in the main supermarkets in Poland. It was found that the detected mean levels of organochlorine residues in tea leaves ranged from ?1 dry weight. Among hexachlorocyclohexane isomers, γ-HCH in green tea occurred in the highest concentrations. Among dichlorodiphenyltrichloroethane (DDT) metabolites the highest level of p,p′DDT (1.96 ng g^?1 dw) was in green tea samples. The transfer of OCPs from tea leaves to brew was investigated. The present study revealed that during the infusion process, a significant percentage of the residues, particularly pesticides with high water solubility, were transferred to the infusions. The obtained results show that the percentage transfer of each pesticides from tea to the tea infusions ranged from 6.74% (heptachlor) to 86.6% (endrin). The detected residues were below current MRLs for these pesticides.     

Irreversible sediment formation in green tea infusions

The formation of irreversible tea sediment (IRS) and its chemical components in green tea infusions were investigated. The results showed that the amounts of IRS in the green tea infusions from various tea cultivars ranged from 0.10 to 1.47 mg/mL. The amount of IRS was influenced remarkably by the chemical components in the green tea infusion. Principal component analysis and regression analysis indicated that gallated catechins, Mn, Ca, caffeine, Na, and (-)-gallocatechin gallate (GCG) were the principal components. IRS (mg/mL) = -4.226 + 0.275 gallated catechins + 79.551 Na + 7.321 Mn + 21.055 Ca + 0.513 caffeine - 0.129 GCG (R2 = 0.697). The contents of the main chemical components in the reversible tea sediment (RTS) and IRS were markedly different, especially the minerals. Large amount of minerals participated in the formation of irreversible green tea sediment. The amount of IRS increased with the extraction temperature.     

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.     

亚太地区茶及类茶植物饮料(草药茶)发展现状及趋势

茶及类茶饮料是近20年来在亚、太地区流行的一种低糖型饮料。由于其醇和甘爽的口感及极富特色的鲜量色调，深度青少年及女性青睐。而其抗氧化、降血脂、消炎灭菌及预防糖尿病等多种保健功能也使中、老年饮者逐渐接受。在分析茶饮市场、预测其流行趋势同时，向读者推荐一批具有巨大市场潜力茶饮之原料，供商家参考。     

Comparison of the main compounds in Fuding white tea infusions from various tea types

The purpose of this study was to compare the main components, and particularly catechins, caffeine, theanine, free amino acids, and water extracts, in Bai Hao Yin Zhen, Bai Mu Dan, and Shou Mei Fuding white tea infusions brewed at different temperatures, and their contributions to taste were estimated by dose-over-threshold value. Infusion temperature had a distinct effect on the main components extracted, and 100 °C was found to be optimal for extracting catechins and caffeine. However, the effect of temperature on theanine, free amino acids, and water extracts varied with tea type. Bai Mu Dan and Shou Mei yielded a higher content of the major compounds than did Bai Hao Yin Zhen. Thus, infusion temperature had a large effect on extracting the main compounds, and the differences in content between the three white teas presumably reflected differences in the harvest time, processing method or leaf shape.     

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.     

广式凉茶研究进展

随着凉茶被列为第一批国家非物质文化遗产名录,其市场迅速扩展,效益显著提高。查阅了近10年来有关凉茶的研究成果,对凉茶定义背景、分类、功效、安全性、生产工艺以及发展前景等方面进行了概述。     

Semi-automatic methods of evaluating the quality of tea infusions

The Roberts & Smith procedure for determining poly phenols and colour in tea infusions has been adapted to semi-automatic operation at the rate of 40 samples per hour. Several modifications have been made, especially in the theaflavin determination, These have not affected reproducibility, and results by the two methods have shown adequate correlation. Examples are given of the application of the method to the constituents of a tea blend; the optical density values for the blend are predictable from the values for the individual teas. Individual garden teas show wide variations in polyphenol content; these variations have not yet been correlated with organoleptic properties.     

Determination of essential and non-essential elements in various tea leaves and tea infusions consumed in Turkey

Tea is one of the most popular beverages in the world. Thus, the chemical components in tea are of great interest, especially in relation to health. In this study, 12 tea samples (10 black, 1 white and 1 green) and 5 herbal tea samples were purchased from supermarkets in Izmir, Turkey. Sample preparation has been performed using wet and microwave digestion procedures. The elemental content (Fe, Zn, Cu, Mn, Ni, Na and K) in the digests and infusions has been analysed. Generally, elemental contents in tea leaves were found to be higher than those in tea infusions. The accuracy of the method was checked and confirmed by standard reference material analyses. The comparison of wet and microwave digestion has not shown significantly different results. Therefore, the microwave digestion procedure was preferred because it is less laborious. The elemental intake related to tea consumption has also been studied.     

Consumers’ associations with herbal infusions and home preparation practices

The consumption of infusions is affected by many factors, namely those associated with culture, health and sensory properties. The main goal of this research was to explore and understand consumers’ perceptions and behaviours regarding consumption and preparation of herbal infusions, applying a mixed methodology: the evaluation of consumers’ behaviours, assessed through direct self-reported measures, and indirect methods, such as free word association and auto-videography. A total of 489 Portuguese consumers replied to a web-based questionnaire. Based on their frequency of consumption and availability, 60 participants were selected for an observational study. Over 27% of the participants had at least a daily cup of herbal infusion, and over 74% had it at least every week. At home, participants reported the use of teapots (44.1%) or mugs/cups (52.0%) to prepare their infusions, and mostly chose bags (77.7%). Approximately 80% of the respondents removed the bags or loose leaves after steeping, mainly based on the infusion colour (53.1%). The freeword association results show that daily and weekly consumers establish a stronger connection with the sensory, emotional, health and wellbeing dimensions of the product, while less frequent consumers only consider the composition of the herbal infusion. From the observational study, it was noticeable that most of the consumers take less than one minute to steep the infusions, clearly below the four to ten minutes recommended for the most popular herbal infusions, like lemon verbena or peppermint. These results emphasize the need for communication strategies focused on the preparation process to give consumers tools to improve their sensory experience.     

浅析广东的凉茶文化及其流变

凉茶是广东地区不可缺少的饮料，因其药性寒凉，功能清热降火，故称之为“凉茶”。广东独特的气候环境和饮食习惯与凉茶有着密切的关系，可以说凉茶是广东一种独特的饮食文化，它把传统的中国茶饮和药物保健结合一体，成为著名的健康饮品。广东因“王老吉凉茶”成为凉茶文化的发源地，而“黄振龙凉茶”则是今天广东凉茶文化兴盛的标志。凉茶影响着广东人民的健康与生活，它已发展为一种产业，影响着国内外的饮料市场。