Definition:
Chlorophyll in tea is the magnesium-containing porphyrin pigment responsible for green colouration in tea leaves, existing as chlorophyll a (blue-green, dominant) and chlorophyll b (yellow-green, minority), with shade-grown teas producing significantly elevated chlorophyll as a light-capture adaptation — this shade response explains why gyokuro and matcha are darker, more vividly green than sun-grown sencha — and its preservation during processing requires the kill-green step (shaqing in Chinese; fixing in English) to deactivate chlorophyllase, the enzyme that would otherwise break down chlorophyll to olive-brown pheophytin. Anji Baicha represents an extreme case: a cultivar with a temperature-sensitive genetic block on chlorophyll synthesis below approximately 23°C, causing near-white spring leaves with altered chemistry.
In-Depth Explanation
Chlorophyll a and b:
| Form | Colour | Absorption Peak | Proportion in Tea |
|---|---|---|---|
| Chlorophyll a | Blue-green | ~430nm, ~680nm | ~70–75% of total |
| Chlorophyll b | Yellow-green | ~455nm, ~640nm | ~25–30% of total |
| Total (shade) | Vivid dark green | — | Much elevated vs. sun |
The a:b ratio shifts under shade conditions — plants shade-adapted to capture diffuse light for photosynthesis produce proportionally more chlorophyll b, which captures different light wavelengths. This is why shade-grown leaves look qualitatively different in colour depth, not just intensity.
Shade growing and chlorophyll production:
Under shade cloth or straw coverage (typically 2–6 weeks for gyokuro; 3–4 weeks for kabusecha), the tea plant is deprived of direct sunlight. To compensate and maintain photosynthesis:
- Chlorophyll synthesis increases dramatically (often 1.5–2x greater than sun-grown)
- The plant also suppresses catechin production (reducing bitterness/astringency)
- Amino acid accumulation increases, especially L-theanine
- Result: darker, more vivid green leaves with less astringency and more umami
Kill-green and chlorophyll preservation:
Immediately after harvest, tea leaves contain the enzyme chlorophyllase, which breaks chlorophyll down into pheophytin (olive) and phytol. The kill-green process (pan-firing for Chinese greens; steaming for Japanese greens) denatures this enzyme at high temperature, locking in green colour. Two outcomes of inadequate kill-green:
- Yellow or olive-tinted tea (enzyme partially active during slow processing)
- Dull, non-vivid colour in final product
Traditional Chinese sun-drying (sun-dried maocha for pu-erh) deliberately allows some chlorophyll conversion — this contributes to pu-erh’s distinctive yellow-green then brown colour evolution with age.
Matcha and chlorophyll as quality signal:
In matcha, colour is a primary quality indicator. High-quality matcha from shade-grown tencha has vivid, jewel-like green — a result of elevated chlorophyll plus preserved health by immediate grinding. Lower-quality matcha, or improperly stored matcha (UV and heat degrade chlorophyll further into pheophorbide and pyropheophytin), becomes dull, yellow-chartreuse. Storing matcha airtight, dark, and cold preserves chlorophyll integrity.
Anji Baicha — the albino exception:
Anji Baicha is a Chinese cultivar (Camellia sinensis ‘Bai Ye 1’) with a temperature-conditional genetic mutation affecting the chlorophyll synthesis pathway. Below ~23°C (spring conditions), the leaves emerge nearly white or very pale yellow-green due to chlorophyll synthesis suppression. Above that temperature, the pathway activates and leaves turn normal green. The albino spring growth is prized for its different chemical profile — extremely high L-theanine, very low catechins, gentle taste — precisely because the leaf is investing biochemically differently than it does in summer. As temperatures rise through spring, Anji Baicha leaves visibly transform from white/pale to green across the same plant.
Chlorophyll in oolong and black teas:
- Oolong: partial oxidation changes surface chlorophyll; green-style oolongs (lighter oolongs like Ali Shan Oolong) retain green tones; darker roasted oolongs have little chlorophyll signal remaining
- Black tea: full oxidation + heat processing converts all chlorophyll; colour of black tea infusion comes entirely from theaflavins and thearubigins
Research
Chlorophyll under shade cultivation:
Kfoury, N., et al. (2018). “Striking changes in tea metabolites due to shade.” Food Chemistry, 272, 485–492. Documents the increase in chlorophyll a and b content and corresponding decrease in catechins under shade conditions in commercially cultivated tea.
Anji Baicha chlorophyll genetics:
Ma, C., et al. (2018). “Transcriptomic and metabolomics analysis of ‘Anji Baicha’ during the natural whitening process in spring.” Frontiers in Plant Science, 9, 738. Characterises the temperature-sensitive chlorophyll synthesis pathway and the resulting amino acid accumulation in the albino growth phase.