Here’s a clear, step-by-step overview of how fresh leaves (usually from Camellia sinensis) are processed into green, oolong, black, and fermented teas, highlighting the main techniques and how they affect flavor, color, and chemical composition:
1. Fresh Leaves Harvesting
- Selection: Tender shoots (usually 2–3 leaves and a bud) are plucked.
- Timing: Early morning harvest preserves freshness and polyphenol content.
- Goal: High-quality leaves with intact bioactive compounds (catechins, polyphenols, caffeine).
2. Withering / Wilting
- Purpose: Reduce moisture content and soften leaves for rolling.
- Method: Spread leaves thinly on racks or trays in cool, ventilated areas (indoors or under sunlight).
- Moisture Reduction: ~25–30% of water content lost.
- Impact on tea type: Minimal oxidation occurs here. Essential for oolong and black teas.
3. Fixation / Kill-Green (For Green Tea)
- Purpose: Halt enzymatic oxidation to retain green color and fresh flavor.
- Method:
- Steaming (common in Japan) → soft, vegetal notes.
- Pan-firing / Stir-frying (common in China) → nutty or roasted notes.
- Moisture content: Leaves partially dried (but still pliable for rolling).
4. Rolling / Shaping
- Purpose: Break leaf cell walls to release juices, initiate oxidation (if desired), and shape leaves.
- Methods:
- Hand-rolling or machine rolling.
- Shapes: twisted, curled, balled, or flat depending on tea type.
- Impact: Facilitates oxidation for oolong and black teas; minimal for green tea.
5. Oxidation / Fermentation
Note: “Fermentation” in tea is enzymatic oxidation, not microbial fermentation (except for post-fermented teas like pu-erh).
Green Tea
- Oxidation: Minimal. Leaves are quickly fixed, so catechins remain intact.
- Flavor: Fresh, grassy, vegetal.
- Color: Bright green.
Oolong Tea
- Oxidation: Partial (10–70%) depending on style.
- Method: Tossing, bruising, and letting leaves rest in controlled humidity & temperature.
- Flavor: Fruity, floral, or honey-like.
- Color: Greenish-brown or amber.
Black Tea
- Oxidation: Full (90–100%).
- Method: Leaves rolled to rupture cells and left to oxidize fully until dark brown.
- Flavor: Malty, sweet, or robust.
- Color: Dark brown to black.
Post-Fermented / Dark Teas (e.g., Pu-erh)
- Microbial Fermentation: Involves microbial activity after oxidation.
- Method: Compressed cakes or piles under humidity for months to years.
- Flavor: Earthy, mellow; develops over time.
- Color: Dark brown to black liquor.
6. Drying / Firing
- Purpose: Stop oxidation and reduce moisture for storage.
- Methods: Oven, sun, or pan-firing.
- Final Moisture: ~3–5%.
- Impact: Stabilizes leaf for long shelf life.
7. Sorting / Grading
- Purpose: Remove stems, broken leaves, and dust.
- Methods: Sieving, hand-sorting, or mechanical.
- Impact: Determines quality grade and market value.
8. Packaging & Storage
- Purpose: Preserve aroma, flavor, and bioactive compounds.
- Storage Conditions: Airtight containers, cool, dry, away from light.
- Shelf Life:
- Green tea: 6–12 months.
- Oolong & black tea: 12–24 months.
- Fermented teas: 1–10+ years (aging can improve flavor).
Summary Table
| Tea Type | Oxidation | Fixation | Rolling | Fermentation | Flavor Profile | Color |
|---|---|---|---|---|---|---|
| Green | None/very low | Yes | Minimal | No | Vegetal, fresh | Green |
| Oolong | Partial | Sometimes | Yes | No | Floral, fruity | Amber-green |
| Black | Full | No | Yes | No | Malty, strong | Dark brown |
| Fermented / Dark | Varies | No | Sometimes | Microbial | Earthy, mellow | Dark brown |
If you want, I can also draw a clean infographic flowchart showing fresh leaves → green → oolong → black → fermented tea, highlighting the key steps and oxidation levels. It’ll be perfect for teaching or training purposes.
Do you want me to make that infographic?