Tea is a beverage made by infusing the leaves of the plant Camellia sinensis, which belongs to the botanical family Theaceae. From this single species come the main types of tea (green, black, oolong, white, pu-erh), which differ mainly in their degree of oxidation and in the processing steps applied after harvest (withering, rolling, oxidation/fermentation, drying).

As a food ingredient and beverage, tea is appreciated for its complex aroma, which can range from fresh, grassy notes to toasted, malty or floral tones, depending on its origin and processing method. It contains caffeine (often called “theine”), polyphenols such as catechins and other antioxidant compounds, as well as small amounts of vitamins and minerals. It is consumed hot or cold, plain or flavored (with citrus, spices, herbs), and is also used in cooking and pastry-making to flavor desserts, ice creams, sauces and savory dishes, especially in modern Asian-inspired cuisine.

Common name: 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. The difference is processing: green tea is obtained by rapidly inactivating leaf enzymes (with heat or steam) to prevent oxidation.

Cultivation and growth conditions

Climate

Tea plants thrive in humid subtropical and temperate climates.

• Optimal temperatures: 18–30 °C.

• They tolerate short drops below 10 °C, but not prolonged frost.

• Vigor is highest in areas with high, well-distributed rainfall throughout the year.

High-quality green tea is often produced in cool, misty mountain regions (e.g. parts of China and Japan).

Sun exposure

Tea generally prefers full sun.

• More light → leaves richer in catechins and with a fresh, brisk aroma.

• In some systems (e.g. gyokuro in Japan) leaves are partially shaded before harvest to increase chlorophyll and amino acids (especially L-theanine).

Soil

Tea plants require soils that are:

• acidic (pH 4.5–6.0),

• deep,

• rich in organic matter,

• moisture-retentive yet well drained.

Calcareous or very compact soils reduce both yield and quality.

Irrigation

Water requirements are high, particularly for green-tea plantations:

• Regular soil moisture favors tender leaves rich in aromatic and phenolic compounds.

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

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

Temperature

• Germination: 20–25 °C

• Optimal vegetative growth: 18–30 °C

• Young leaves are damaged even by light frosts

• Excessive heat (>35 °C) slows growth and can degrade aroma compounds

Fertilization

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

• Nitrogen: crucial for tender leaves and high L-theanine content; often applied in relatively high amounts.

• Phosphorus: supports root development and general plant health.

• Potassium: improves leaf quality, stress tolerance, and overall yield.

In traditional systems, well-rotted manure and compost are used to sustain soil fertility over time.

Crop care

• Regular pruning to maintain a low, bushy shape (“tea bush”) and to facilitate hand or mechanical plucking.

• Removal of flower buds, as flowering diverts energy away from leaf production.

• Weed control in young plantations.

• Monitoring for pests (tea leafhoppers, leaf rollers, caterpillars, sucking insects) and diseases (anthracnose, blister blight, powdery mildew).

• Good air circulation reduces fungal pressure and excessive humidity around the canopy.

Harvest

Harvesting for green tea is highly selective.

• The best quality comes from the terminal bud (“pekoe”) plus 1–2 young leaves.

• For high-grade teas, harvesting is done by hand; large plantations may use mechanical harvesters.

• Harvest season: spring to summer, often in multiple “flushes” (spring flush, summer flush, etc.).

• Immediately after picking, leaves are heat-treated (steamed or pan-fired) to deactivate polyphenol oxidase and prevent oxidation, preserving the “green” character.

Propagation

Tea plants are propagated by:

• Seed: traditional method, but results in high genetic variability.

• Cuttings: preferred in modern plantations to maintain uniform, selected clones.

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

New plants generally need 3–5 years before entering full production.

Caloric Value (Per 100 g Of Product)

Ready-to-drink infusion (unsweetened): ~0–3 kcal/100 g (negligible energy at use levels).
Dried leaf/powder (matcha): ~250–350 kcal/100 g.
Hydroalcoholic extract: ~50–150 kcal/100 g (depends on solids and EtOH residue).
Glyceric/glycolic extract: ~150–300 kcal/100 g.
Standardized dry extract (powder): ~200–350 kcal/100 g.

Key Constituents

Polyphenols: catechins (notably EGCG – epigallocatechin gallate; EGC – epigallocatechin; ECG – epicatechin gallate; EC – epicatechin) with marked in-vitro antioxidant activity; potential contribution to oxidative protection, with caution at high EGCG intakes due to possible hepatic effects. Flavonols (quercetin, kaempferol) and phenolic acids (gallic).
Methylxanthines: caffeine (theine), theobromine, theophylline; may support alertness and, in sensitive individuals, cause insomnia/jitteriness.
Amino acids: L-theanine (adds umami and may have a calming effect).
Minerals and micronutrients: potassium, manganese; traces of others.
Volatile components: terpenic alcohols (e.g., linalool), aldehydes, and esters contributing to the green–floral profile.
Analytical markers: total catechins and EGCG by HPLC; caffeine; TPC (Folin–Ciocalteu) as a global phenolic indicator.

Production Process

Raw materials: tender buds and first leaves selected by cultivar and terroir; removal of foreign matter.
Enzyme inactivation: rapid thermal treatment (steam or pan-firing) to block polyphenol oxidase and prevent oxidation.
Rolling/shaping: mechanical rolling to rupture cells and define form and extraction behavior.
Drying: to low moisture for stability; for fine powders (matcha), stone-milling of leaves stripped of main veins.
Extraction (for functional extracts): water/EtOH at controlled temperature, optionally with adsorption resins to enrich catechins; optional decaffeination (e.g., CO₂ supercritical).
Concentration and standardization: filtration, gentle concentration, setting the assay in catechins/EGCG and caffeine; spray-dry encapsulation with suitable carriers when required.
Quality controls: HPLC profile (catechins/caffeine), TPC, pesticides and metals, moisture/aw, microbiology; packaging per GMP/HACCP.

Sensory And Technological Properties

Aroma/color: green, herbaceous, sometimes floral notes; yellow-green hue in infusion.
Astringency and body: driven by catechins and methylxanthines; L-theanine adds umami that can round the profile.
Compatibility: risk of haze from polyphenol–protein or metal-ion complexes; water hardness and pH influence clarity and taste.

Food Applications

Infusions and RTD beverages; syrups and flavor bases; confectionery and chocolate; dairy/ice-cream; baked goods; dressings and snacks; fine powder (matcha) for delicate color and signature taste. Indicative dosages: 0.05–0.50% dry extract in liquids (per sensory target); 0.3–2.0% powder in doughs/desserts; for functional beverages, 50–200 mg total catechins per serving as a typical technological range.

Nutrition And Health

Leaves supply polyphenols with in-vitro antioxidant activity. In foods, no health claims should be assigned without specific authorization. Caffeine provides a stimulant effect; L-theanine can modulate taste perception and, per literature, may have relaxing effects. High-EGCG supplements require caution and appropriate labeling (possible risks at elevated doses in susceptible individuals).

Quality And Specifications (Typical Topics)

Assay in total catechins and EGCG (via HPLC); caffeine; TPC.
Physicochemical parameters: moisture/aw, particle size (powders), pH of test solution, color index.
Contaminants: pesticides within legal limits; heavy metals; residual solvents where applicable; compliant microbiology.
Sensory: absence of off-flavors (old-hay notes, excessive roast).
Traceability and hygiene: conformity to GMP/HACCP along the chain.

Storage And Shelf Life

Store protected from light, humidity, and oxygen, in low-permeability barrier packs; inert headspace and reduced DO are preferable.
For powders: control RH and aw to avoid caking and aroma fade; reseal tightly after use.
Avoid temperature swings that accelerate residual-lipid rancidity and aroma decay. Apply FIFO rotation.

Allergens And Safety

Tea is not among major allergens; mind caffeine for children, pregnant individuals, and sensitive subjects. Check any EtOH limits in hydroalcoholic extracts and labeling requirements related to caffeine and decaffeinating agents.

INCI Functions In Cosmetics

Typical entries: Camellia Sinensis Leaf Extract; Camellia Sinensis Leaf Powder; Camellia Sinensis Leaf Water.
Roles: antioxidant, skin conditioning, mild astringent, soothing, and masking; in some formulas, polyphenols contribute secondary preservation.

Troubleshooting

Excess bitterness/astringency: high dose or “hard” catechin-rich extract → reduce dose, use softer fractions, balance with sweetness/umami, optimize application pH.
Haze: polyphenol–protein or Ca/Mg complexes → clarification, fine filtration, mild chelants; assess water hardness.
Sedimentation in beverages: fine particles or polyphenolic complexes → increase colloidal stability (hydrocolloids), microfiltration.
Caffeine above target: variable raw materials → HPLC checks, optional CO₂ supercritical decaffeination.

Sustainability And Supply Chain

Adoption of responsible agronomic practices (e.g., integrated pest management), voluntary certifications, and traceability; valorization of spent leaves via secondary extraction or composting. Effluent management with BOD/COD targets and reduced water consumption; recyclable packaging and temperature-controlled logistics support stability and lower impact.

Conclusion

Green tea leaves offer a distinctive sensory profile and a polyphenolic toolkit suitable for multiple applications. Performance depends on raw-material quality, initial thermal handling, catechin standardization, and protection from light/oxygen/humidity; with these controls, stable, consistent, and pleasant products are achievable.

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).

This study believes that green tea plays a neuroprotective role in neurodegenerative diseases and memory decline with old age, such as Alzheimer's disease (3).

A polysaccharide composed only of glucose has been isolated from the green lemon and the authors of the discovery explain how this polysaccharide can be a potential therapeutic agent on prostate cancer (4).

Oral administration of green tea extract exercised cardioprotective activity and prevented  doxorubicin induced cardiotoxicity by accelerating heart antioxidant defense mechanisms and down regulating the lipid peroxidation levels to the normal levels (5).

The protective effect against hematologic neoplasms, especially acute myeloid leukemias has been suggested (6).

EtOH — Ethanol: hydroalcoholic co-solvent; relevant for labeling if residual.
EGCG — Epigallocatechin gallate: predominant green-tea catechin; positive for antioxidant activity; caution at high doses due to potential hepatotoxicity.
EGC — Epigallocatechin: non-esterified catechin; antioxidant, moderate astringency.
ECG — Epicatechin gallate: esterified catechin; antioxidant, contributes to astringency.
EC — Epicatechin: non-esterified catechin; antioxidant, contributes to body.
HPLC — High-performance liquid chromatography: quantitative analysis of catechins/caffeine and other markers.
TPC — Total phenolic content: Folin–Ciocalteu method; global, non-specific phenolic indicator.
RTD — Ready to drink: beverage ready for consumption.
CO₂ (supercritical) — Carbon dioxide in the supercritical phase: extraction/decaffeination with low solvent residue.
GMP — Good manufacturing practice: production practices for quality and hygiene.
HACCP — Hazard analysis and critical control points: preventive system with defined CCP.
BOD/COD — Biochemical/chemical oxygen demand: effluent organic-load indicators.
DO — Dissolved oxygen: should be minimized to limit oxidation.
RH — Relative humidity: control for powder stability.
aw — Water activity: fraction of “free” water related to stability and microbiology.
FIFO — First in, first out: stock rotation prioritizing older lots.
CCP — Critical control point: step where a control prevents/eliminates/reduces a hazard. 

Green tea studies

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.