Green Tea

Botanical Profile

Green tea is obtained from the leaves of Camellia sinensis, an evergreen shrub or small tree of the Theaceae. The species is one of the world's most important cultivated beverage plants and forms the botanical basis of green, black, white, oolong and other tea types; their differences arise primarily from cultivar, harvest and processing.

Camellia sinensis is native to parts of East, South and Southeast Asia and has been cultivated for centuries in China, Japan, India and many other regions. Commercial tea plants are regularly pruned to maintain a low harvesting table and promote young shoots.

The leaves are leathery, glossy and serrated; young shoots and buds are particularly important for high-quality teas. Small white flowers with numerous yellow stamens develop into capsules. Two broad cultivated groups, var. sinensis and var. assamica, differ in morphology, climate adaptation and use.

Green tea is produced by rapidly inactivating endogenous enzymes after harvest, traditionally by steaming or pan heating. This limits enzymatic oxidation of polyphenols and distinguishes green tea chemically and sensorially from more strongly oxidised tea types.

For raw-material quality, origin, cultivar, harvest grade, leaf age, processing, particle size, moisture, pesticide residues, contaminants and storage conditions are relevant. Tea is therefore both a botanical raw material and a highly processing-dependent product.

Phytochemistry

The characteristic constituents of green tea include catechins, caffeine, amino acids, flavonols, phenolic acids, volatile aroma compounds, chlorophylls, carotenoids, minerals and polysaccharides. Important catechins include epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate and epicatechin.

The catechin profile is strongly influenced by cultivar, growing conditions, leaf age, shading, harvest time and processing. Because green-tea processing limits enzymatic oxidation, monomeric catechins remain comparatively prominent, whereas black-tea manufacture produces more theaflavins and thearubigins.

Caffeine is another important constituent and contributes to the sensory and physiological character of tea. The amino acid L-theanine is particularly associated with tea and contributes to taste. Volatile compounds determine the aroma and change substantially during heating and drying.

Analytical quality assessment commonly uses HPLC or LC-MS for catechins and caffeine, alongside tests for moisture, identity, residues, heavy metals and microbiological quality. Extracts can differ markedly from leaf tea depending on solvent, drug-extract ratio, concentration and standardisation.

Traditional Uses

Tea has a very long cultural history in East Asia. In China it developed from an early plant preparation into a sophisticated beverage culture; from there cultivation, processing and tea customs spread to Japan, Korea and later throughout the world.

Green tea became embedded in everyday life, hospitality, monastic traditions, ceremonial practice and trade. Regional processing methods created distinctive styles, from steamed Japanese green teas to pan-fired Chinese teas.

Historically, tea was valued as a beverage for taste, aroma, social ritual and its characteristic stimulating quality. The traditional context is therefore broader than a medicinal-use narrative and includes agriculture, craftsmanship, cuisine and cultural identity.

For a public-facing botanical profile, green tea should be presented as a globally important beverage and botanical raw material with a long East Asian cultural tradition and a well-characterised phytochemical profile.

Current Research

Modern research on Camellia sinensis is extensive and covers plant genetics, cultivation, processing, catechin chemistry, caffeine, L-theanine, aroma formation, food technology and analytical standardisation.

A major research field concerns the stability and transformation of catechins during extraction, heating, storage and digestion. EGCG is one of the most intensively studied tea constituents, while the relationship between whole-tea matrices and isolated constituents remains an important scientific distinction.

Agronomic studies investigate cultivar selection, shading, climate effects, drought, soil conditions and harvest management. Food-technology research examines steaming, pan firing, rolling, drying, fermentation and storage and their effects on sensory and chemical quality.

For extracts, standardisation, solvent systems, caffeine content, catechin profile and contaminant control are particularly relevant. Scientific findings must be distinguished from legally permissible product claims and assessed in the context of the specific preparation.

Sources

• Plants of the World Online. Kew Science. Royal Botanic Gardens, Kew: Camellia sinensis (L.) Kuntze.
• European Pharmacopoeia and pharmacognostic literature on tea leaf.
• PubMed-indexed literature on green-tea catechins, EGCG, caffeine and L-theanine.
• Food-chemistry literature on tea processing, aroma and polyphenol transformation.
• Botanical and cultural-historical literature on tea cultivation and use in East Asia.