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Black tea is one of the most popular beverages consumed in the world. It is stronger in taste as well as in flavour compared to other less oxidized teas. It is made from the leaves of the shrub Camellia sinensis var. assamica. Black tea can be supplemented with other plant parts to enhance its flavour and health-promoting properties. In India, Ocimum spp. leaves have been used for their medicinal properties since ancient times. These leaves can be added during black tea preparation to enhance their aroma and healing activities. O. gratissimum, known as "Scent Leaf", is traditionally used for the management of many diseases, such as the common cold and cough. This work was designed to evaluate the antioxidant interaction between black tea and O. gratissimum (leaves) at five different ratios (1:1, 1:2, 1:3, 2:1, and 3:1). To determine the antioxidant activity, chemical-based methods and ex vivo assays were conducted. The total phenolic and flavonoid contents were calculated by Folin's reagent and aluminium chloride colorimetric assays, respectively. The antioxidant interactions were determined by the combination index (CI), using CompuSyn software. The black tea exhibited higher radical quenching activity (DPPH, ABTS, and NO) and antihaemolytic and anti-lipid peroxidation potential compared to the Ocimum gratissimum infusion. Variation in the antioxidant capability was observed for various ratios of the black tea and O. gratissimum (BT+OG) combination. The antioxidant interaction between BT and OG ranged from nearly additive to antagonistic. The total phenolic content was higher for O. gratissimum, whereas the total flavonoid content was high in black tea. The binary mixture of BT+OG at all ratios (3:1, 2:1, 1:1, 1:2, and 1:3) expressed similar phenolic and flavonoid levels. Overall, black tea and O. gratissimum displayed additive antioxidant interaction and the highest free radical scavenging potential at a 3:1 proportion in all the performed parameters. [ABSTRACT FROM AUTHOR]

Abstract: The fluoride contents were determined by ion-selective electrode in 26 black tea samples originally produced in Turkey, Sri Lanka, India and Kenya, and in 14 herbal and seven fruit infusions originated from Turkey. Fluoride content in black tea infusions ranged from 0.57 to 3.72mg/L after 5min of brewing. Higher fluoride levels were found in black teas originated from Turkey when compared with teas originated from Sri Lanka. Moreover higher fluoride levels were determined in black tea bags compared with granular and stick-shaped black teas. However, herbal and fruit infusions were characterized by low values of fluoride (0.02–0.04mg/L) after 5min of brewing and increasing brewing time to 10min caused only slight increases in some infusions. As a result, consuming tea infusions prepared from some black tea available in Turkish market, especially black tea bags, in large quantities may lead to exposion to a high amount of fluoride which may cause dental fluorosis. Although fruit and herbal infusions are safer to consume their fluoride contents are too low for caries prevention. In countries such as Turkey where tea is traditionally consumed, the fluoride concentration and daily safety precautions should be indicated on tea products. [Copyright &y& Elsevier]

Abstract: Tea is the most popular beverage in the world. Since tea contains several essential nutrients, drinking of tea is considered beneficial for human health. The presence of heavy metals in trace level in tea has received special attention because they are directly related to health. A basket survey was conducted in the tea districts of south India to generate a data base on the presence of heavy metals in black tea. A total of one hundred black tea samples, collected from the tea growing regions of Valparai and Nilgiris in Tamil Nadu, Vandiperiyar, Wayanad and Munnar in Kerala and Karnataka state were analyzed for heavy metals. The results of analysis showed that the mean level of Cu was 24.07±2.25mgkg−1, Cr 4.76±1.27mgkg−1, Ni 2.53±1.01mgkg−1, Cd 0.14±0.06mgkg−1 and 0.81±0.32mgkg−1. Under the Prevention of Food Adulteration Act (PFA) of India the tolerance limits have been fixed only for copper and lead. The present database could be used for fixing tolerance limits of the other heavy metals in tea. The contents of copper and lead in tea were below the permissible limit under the PFA act. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

The article discusses the scope and limitation of the taste sensor system for analyzing the astringency of black tea samples manufactured in India and Sri Lanka. According to the results of an organoleptic test, the sensor output was correlative to the human gustatory sense. The authors conclude that the astrigency of black tea can be successfully evaluated by using a 0.65 mM and 0.26 mM epigallocatechin-3-O-gallate aqueous solution including 5 mM KCl as a standard.

Background: Tea, a commonly consumed beverage, contains high amounts of polyphenols that can impair protein digestibility, as demonstrated in vitro. There are no human studies examining the inhibitory influence of tea polyphenols (TPP) on high-quality protein digestibility., Objective: The aim of this study was to determine the effect of black tea on the true indispensable amino acid (IAA) digestibility of whole boiled egg protein, in healthy adult humans, through use of a dual isotope tracer approach., Methods: The effect of black TPP (4.6 mg/mL, ingested as a beverage with the meal) on 2H-labeled whole boiled egg protein, administered with ghee rice and tomato curry, was measured with reference to 13C-spirulina protein in healthy Indian adults aged 20-27 y of both sexes with BMI of 22.0 ± 2.8 kg/m2. The results were then compared to previously determined whole egg mean IAA digestibility measured by the same method, without black tea, in the same subjects (n = 5). To correct for any independent effect of TPP on spirulina protein (used as a standard protein), the true IAA digestibility of 13C-spirulina protein was independently measured with reference to a 2H-amino acid mixture, with and without co-ingestion of black tea, in 3 of the same subjects., Results: The true IAA digestibility of whole boiled egg protein significantly decreased by 17% when co-ingested with black tea. However, there was no significant reduction in the true IAA digestibility of spirulina protein when co-ingested with black tea., Conclusions: TPP protein interactions reduced whole egg digestibility in healthy Indian adults but had minimal effect on spirulina protein digestibility. In populations who are at risk of dietary quality protein inadequacy, the consumption of tea during or after a meal can further increase the risk of inadequacy. This trial was registered at Clinical Trials Registry of India (http://ctri.nic.in) as CTRI/2018/03/012265., (Copyright © American Society for Nutrition 2019.)

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.