Black tea, known as "red tea" (红茶) in China due to the color of its brewed liquid, is the most oxidized of all tea types. Oxidation is a process that exposes the tea leaves to air, which results in the darkening of the leaves and the development of richer flavors.

Common name: Black tea

Parent plant: Camellia sinensis (L.) Kuntze

Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Order: Ericales
Family: Theaceae
Genus: Camellia
Species: Camellia sinensis (L.) Kuntze

Note: Green, black, white, and oolong tea all come from the same species. Black tea is obtained through full enzymatic oxidation of the leaves, which become dark and develop a stronger, more malty and tannic aroma.

Cultivation and growth conditions

Climate

The tea plant thrives in humid subtropical and temperate climates.

• Optimal temperatures: 18–30 °C.

• It does not tolerate prolonged frost.

• Vigorous growth in regions with high, well-distributed rainfall throughout the year.

Mountain and highland areas (e.g. Himalayas, Sri Lanka, East Africa) often produce very aromatic black teas thanks to cool nights and high humidity.

Sun exposure

Tea generally prefers full sun, which:

• increases polyphenol content,

• promotes vigorous shoot growth,

• improves yield.

In many high-altitude regions, light is intense but temperatures stay relatively cool, which is ideal for high-quality black tea.

Soil

Tea plants require soils that are:

• acidic (pH 4.5–6.0),

• deep,

• rich in organic matter,

• well drained yet capable of holding moisture.

Calcareous or very compact soils reduce both productivity and leaf quality.

Irrigation

Water requirements are medium to high:

• Regular moisture favors tender shoots rich in aromatic compounds.

• Waterlogging must be avoided to prevent root and collar rots.

• In intensive systems, supplemental irrigation is often used during dry periods.

Temperature

• Germination: 20–25 °C

• Optimal vegetative growth: 18–30 °C

• Young leaves are sensitive even to light frost

• Excessive heat (>35 °C) reduces aroma quality and slows growth

Fertilization

Tea is a nutrient-demanding crop, especially for black tea production.

• Nitrogen: essential for tender leaves and high yields.

• Phosphorus: supports rooting and overall vigor.

• Potassium: improves leaf quality, stress resistance, and cup character.

Organic compost and manures are widely used to maintain long-term soil fertility.

Crop care

• Regular pruning to keep the bushes low and flat (“tea table”), facilitating plucking.

• Removal of flowers, since flowering diverts energy away from leaf production.

• Weed control, especially in young plantations.

• Monitoring for pests (tea leafhoppers, sucking insects, caterpillars) and diseases (anthracnose, blister blight, other fungal spots).

• Good air circulation in the canopy reduces disease pressure.

Harvest

Harvest for black tea is selective but often slightly less strict than for high-end green tea.

• Typically the terminal bud (“pekoe”) plus 2–3 leaves are plucked.

• Hand plucking for high-quality teas; mechanical harvesting in large estates.

• Multiple seasonal harvests (“flushes”), with particularly prized spring and monsoon flushes in some regions (e.g. Darjeeling).

After harvesting, leaves undergo:

1. Withering

2. Rolling (or CTC shredding)

3. Full oxidation (often incorrectly called “fermentation”)

4. Drying and sorting.

Propagation

Tea plants are propagated by:

• Seed: traditional method, gives genetically variable plants.

• Cuttings: preferred in modern plantations to obtain uniform, clonal material.

• Layering (marcotting): used locally in some traditional systems.

Young plants usually enter commercial production after 3–5 years.

Characteristics of Black Tea

• Color: Black tea leaves are dark brown or black. When brewed, the tea generally has a deep amber or dark red color.
• Flavor: Compared to green or white teas, black tea has a stronger, more robust flavor. It can range from malty and sweet to brisk and astringent.
• Caffeine Content: Black tea generally has a higher caffeine content compared to other teas, typically ranging from 40-70mg per 8 oz cup.

Popular Varieties of Black Tea

• Assam: Originates from Assam, India. It has a bold, brisk, and malty flavor and is often used in breakfast blends.
• Darjeeling: From the Darjeeling region of India, it has a delicate aroma and can vary in flavor with the season of harvest. The "first flush" (spring harvest) is often light and floral, while the "second flush" (summer harvest) can be more robust and fruity.
• Ceylon: From Sri Lanka, previously known as Ceylon. It is known for its brisk and bright character.
• Keemun: A high-quality black tea from China with a wine-like and fruity taste.
• Earl Grey: A flavored black tea infused with the oil of bergamot, a type of citrus fruit.

Processing

After being plucked, the leaves are withered to reduce moisture content. They are then rolled to break down the cell walls and release enzymes, initiating the oxidation process. The leaves are spread out and allowed to oxidize, during which they darken and develop flavor. Finally, the oxidized leaves are dried to stop the oxidation process and preserve the tea.

Health Benefits

Black tea contains antioxidants called flavonoids that are believed to have various health benefits, including supporting heart health. It also contains other beneficial compounds like theaflavins and thearubigins. Regular consumption of black tea has been linked to reduced risk of certain chronic diseases, though it's always essential to consult scientific research and health professionals for specific health claims.

Brewing

Typically, black tea is brewed with boiling water and steeped for 3-5 minutes, though the exact time can vary based on personal preference and the specific variety.

In many cultures, black tea is often enjoyed with milk, sugar, or honey, and sometimes with spices, as in the case of Indian chai.

Black tea studies

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Tea (Camellia sinensis) is a plant widely used for ethnopharmacological use due mainly to the presence of polyphenols such as catechin and its derivatives, anthocyanins, flavonoids.

The color varieties are mainly due to differences in treatment, climate, but basically the variations between plants are few.

It is grown in:

• India
• Cina
• Sri Lanka
• Kenya
• Indonesia

The most common are:

• Black Tea: This is the most commonly consumed tea worldwide, especially in Western countries and South Asia. Examples include Assam, Darjeeling, Ceylon, and Earl Grey. Popular ways of consuming it include English breakfast tea and the chai made in India.
• Green Tea: Especially popular in East Asian countries like China and Japan. Examples include Dragonwell, Sencha, Bancha, Matcha, and Gunpowder. Green tea is also becoming increasingly popular in the West due to its purported health benefits.
• Oolong Tea: This is a partially oxidized tea that sits between black and green tea in terms of oxidation. It's especially popular in China and Taiwan. Examples are Tieguanyin and Wuyi Rock teas.
• White Tea: A lightly oxidized tea that retains a delicate flavor and is often described as sweeter than green or black tea. Bai Mudan (White Peony) and Silver Needle are popular varieties.
• Herbal Tea: Although not true teas (since they aren't derived from the Camellia sinensis plant), herbal infusions are widely consumed. Popular examples include chamomile, peppermint, rooibos, and hibiscus.
• Puerh Tea: This is a type of fermented tea from the Yunnan province of China. It comes in raw (Sheng) and ripe (Shou) varieties and is often pressed into cakes.

The characteristic scent of tea seems to be influenced by the jasmonic acid present in the leaves (1).

When tea is taken to prevent or combat disease, attention should be paid to doses and, as with almost all herbs, ingestion of large amounts may be toxic. When the tea is taken for therapeutic purposes for cardiovascular diseases, diabetes and more, the best results are obtained in people who consume 3-4 cups of tea (600-900 mg of catechins) per day (2).

A study from 2004 to 2014 on elderly people found that frequent consumption of tea can reduce the risk of depressive symptoms (3).

Black tea contains important flavonoids which, according to this in vitro study, exerting an inhibitory effect on colon cancer cells could be better studied to become possible medicines (4).

Facial dermatitis is normally treated with calcineurin inhibitors or corticosteroids. Black tea dressings represent an effective treatment option for facial dermatitis (5).

The addition of milk to black tea in some way modifies the impact on blood pressure and vascular function (6).

Theaflavin e thearubigins, two flavonoids isolated from black tea, have been shown to be useful to relieve hyperglycemia and hypercholesterolemia (7).

References____________________________________

(1) Li J, Zeng L, Liao Y, Gu D, Tang J, Yang Z. Influence of Chloroplast Defects on Formation of Jasmonic Acid and Characteristic Aroma Compounds in Tea (Camellia sinensis) Leaves Exposed to Postharvest Stresses. Int J Mol Sci. 2019 Feb 27;20(5):1044. doi: 10.3390/ijms20051044. 

Abstract. Characteristic aroma formation in tea (Camellia sinensis) leaves during the oolong tea manufacturing process might result from the defense responses of tea leaves against these various stresses, which involves upregulation of the upstream signal phytohormones related to leaf chloroplasts, such as jasmonic acid (JA). Whether chloroplast changes affect the formation of JA and characteristic aroma compounds in tea leaves exposed to stresses is unknown. In tea germplasms, albino-induced yellow tea leaves have defects in chloroplast ultrastructure and composition. Herein, we have compared the differential responses of phytohormone and characteristic aroma compound formation in normal green and albino-induced yellow tea leaves exposed to continuous wounding stress, which is the main stress in oolong tea manufacture. In contrast to single wounding stress (from picking, as a control), continuous wounding stress can upregulate the expression of CsMYC2, a key transcription factor of JA signaling, and activate the synthesis of JA and characteristic aroma compounds in both normal tea leaves (normal chloroplasts) and albino tea leaves (chloroplast defects). Chloroplast defects had no significant effect on the expression levels of CsMYC2 and JA synthesis-related genes in response to continuous wounding stress, but reduced the increase in JA content in response to continuous wounding stress. Furthermore, chloroplast defects reduced the increase in volatile fatty acid derivatives, including jasmine lactone and green leaf volatile contents, in response to continuous wounding stress. Overall, the formation of metabolites derived from fatty acids, such as JA, jasmine lactone, and green leaf volatiles in tea leaves, in response to continuous wounding stress, was affected by chloroplast defects. This information will improve understanding of the relationship of the stress responses of JA and aroma compound formation with chloroplast changes in tea.

(2) Yang CS, Zhang J. Studies on the Prevention of Cancer and Cardiometabolic Diseases by Tea: Issues on Mechanisms, Effective Doses, and Toxicities. Agric Food Chem. 2019 May 15;67(19):5446-5456. doi: 10.1021/acs.jafc.8b05242.

Abstract. This article presents a brief overview of studies on the prevention of cancer and cardiometabolic diseases by tea. The major focus is on green tea catechins concerning the effective doses used, the mechanisms of action, and possible toxic effects. In cancer prevention by tea, the laboratory results are strong; however, the human data are inconclusive, and the effective doses used in some human trials approached toxic levels. In studies of the alleviation of metabolic syndrome, diabetes, and prevention of cardiovascular diseases, the results from human studies are stronger in individuals who consume 3-4 cups of tea (600-900 mg of catechins) or more per day. The tolerable upper intake level of tea catechins has been set at 300 mg of (-)-epigallocatechin-3-gallate in a bolus dose per day in some European countries. The effects of doses and dosage forms on catechin toxicity, the mechanisms involved, and factors that may affect toxicity are discussed.

(3)  Schimidt HL, Garcia A, Martins A, Mello-Carpes PB, Carpes FP. Green tea supplementation produces better neuroprotective effects than red and black tea in Alzheimer-like rat model. Food Res Int. 2017 Oct;100(Pt 1):442-448. doi: 10.1016/j.foodres.2017.07.026.

(4)   Yang K, Gao ZY, Li TQ, Song W, Xiao W, Zheng J, Chen H, Chen GH, Zou HY. Anti-tumor activity and the mechanism of a green tea (Camellia sinensis) polysaccharide on prostate cancer. Int J Biol Macromol. 2019 Feb 1;122:95-103. doi: 10.1016/j.ijbiomac.2018.10.101.

(5)  Khan G, Haque SE, Anwer T, Ahsan MN, Safhi MM, Alam MF. Cardioprotective effect of green tea extract on doxorubicin-induced cardiotoxicity in rats. Acta Pol Pharm. 2014 Sep-Oct;71(5):861-8.

Abstract. The in vivo antioxidant properties of green tea extract (GTE) were investigated against doxorubicin (DOX) induced cardiotoxicity in rats. In this experiment, 48 Wistar albino rats (200-250 g) were divided into eight groups (n = 6). Control group received normal saline for 30 days. Cardiotoxicity was induced by DOX (20 mg/kg ip.), once on 29th day of study and were treated with GTE (100, 200 and 400 mg/kg, p.o.) for 30 days. Aspartate aminotransferase (AST), creatinine kinase (CK), lactate dehydrogenase (LDH), lipid peroxidation (LPO), cytochrome P450 (CYP), blood glutathione, tissue glutathione, enzymatic and non-enzymatic antioxidants were evaluated along with histopathological studies. DOX treated rats showed a significant increased levels of AST, CK, LDH, LPO and CYP, which were restored by oral administration of GTE at doses 100, 200 and 400 mg/kg for 30 days. Moreover, GTE administration significantly increased the activities of glutathione peroxidase (GPX), glutathione reductase (GR), glutathione s-transferase (GST), superoxide dismutase (SOD) and catalase (CAT), in heart, which were reduced by DOX treatment. In this study, we have found that oral administration of GTE prevented DOX-induced cardiotoxicity by accelerating heart antioxidant defense mechanisms and down regulating the LPO levels to the normal levels.

(6) Takada M, Yamagishi K, Iso H, Tamakoshi A. Green tea consumption and risk of hematologic neoplasms: the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study).  Cancer Causes Control. 2019 Aug 26. doi: 10.1007/s10552-019-01220-z.

Abstract. Purpose: Experimental studies suggested that green tea may have an anticancer effect on hematologic neoplasms. However, few prospective studies have been conducted. Methods: A total of 65,042 individuals aged 40-79 years participated in this study and completed a self-administered questionnaire about their lifestyle and medical history at baseline (1988-1990). Of these, 52,462 individuals living in 24 communities with information on incident hematologic neoplasms available in the cancer registry, who did not have a history of cancer and provided valid information on frequency of green tea consumption, were followed through 2009. Hazard ratios (HRs) and 95% confidence intervals (CIs) for the incidence of hematologic neoplasms according to green tea consumption were analyzed. Results: The incidence of hematologic neoplasms during a median follow-up of 13.3 years was 323. Compared with the never-drinkers of green tea, the multivariate HRs and 95% CIs for total hematologic neoplasms in green tea drinkers of ≤ 2 cups/day, 3-4 cups/day, and ≥ 5 cups/day were 0.65 (0.42-1.00), 0.73 (0.47-1.13), and 0.63 (0.42-0.96), respectively. The association was more prominent for acute myeloid leukemias and follicular lymphomas. Conclusions: The present cohort study suggests a protective effect of green tea against hematologic neoplasms, especially acute myeloid leukemias.

Kuriyama S. The relation between green tea consumption and cardiovascular disease as evidenced by epidemiological studies. J Nutr. 2008 Aug;138(8):1548S-1553S. doi: 10.1093/jn/138.8.1548S.

Abstract. Although substantial evidence from in vitro and animal studies indicates that green tea preparations inhibit cardiovascular disease processes, the possible protective role of green tea consumption against this disease in humans remains unclear. We conducted a population-based prospective cohort study (the Ohsaki Study) to examine the association between green tea consumption and mortality from cardiovascular disease (CVD), cancer, and all causes with 40,530 persons in Miyagi prefecture, in northern Japan. Previously published work has shown that green tea consumption was inversely associated with mortality from CVD and all causes. The inverse association of mortality from CVD was more pronounced in women (P = 0.08 for interaction with sex). In women, the multivariate hazard ratios (95% confidence intervals) of CVD mortality across increasing green tea consumption categories were 1.00, 0.84 (0.63-1.12), 0.69 (0.52-0.93), 0.69 (0.53-0.90) (P for trend = 0.004). Within CVD mortality, the stronger inverse association was observed for stroke mortality. Because our observational study has found the inverse association, I report here the results of a review of epidemiological evidence from randomized controlled trials (RCT) of the association between green tea or green tea extracts and CVD risk profiles. More than half of the RCT have demonstrated the beneficial effects of green tea on CVD risk profiles. These results from RCT suggest a plausible mechanism for the beneficial effects of green tea and provide substantial support for our observations.