Fixed green (also called kill-green or, in Chinese, 殺青, shā qīng — literally “kill the green”) is the critical heat-application step in green tea manufacture that deactivates the polyphenol oxidase and peroxidase enzymes responsible for oxidation. By applying heat immediately after plucking (or after a short wither), the tea maker prevents enzymatic browning and locks the leaf chemistry at its fresh-green state. This step is what distinguishes green tea from all other categories: oolong undergoes partial oxidation before kill-green; black tea undergoes full oxidation before kill-green; white tea and yellow tea use minimal heat or delayed heat application.
Also known as: kill-green, shaqing, sha qing, fixation, de-enzyming, firing (in some contexts)
In-Depth Explanation
Immediately after plucking, tea leaf begins to oxidize. Oxygen in the air contacts polyphenol oxidase enzymes within the leaf cells, initiating the same browning reactions seen when a sliced apple or avocado is exposed to air. Without intervention, the leaf would fully oxidize within hours, producing black tea. Kill-green interrupts this process.
Methods of kill-green:
The choice of kill-green method is one of the most significant determinants of a green tea’s flavour character. Two primary methods exist:
| Method | Key examples | Sensory character |
|---|---|---|
| Pan-firing (炒青, chǎo qīng) | Longjing, Bi Luo Chun, most Chinese greens | Toasty, nutty, lighter body, less “grassy” |
| Steaming (蒸青, zhēng qīng) | Most Japanese greens (sencha, gyokuro, matcha) | Vivid green, grassy/vegetal, marine/umami, heavier body |
Pan-firing: The leaf is tumbled or pressed in large, heated pans (or drums in modern factories) at 200–300°C. The high, dry heat rapidly inactivates enzymes and begins to develop Maillard reaction products — toasty, nutty, slightly roasted notes that are characteristic of Chinese pan-fired greens. Longjing’s famous toasty-chestnut character, for example, is primarily from its pan-firing process.
Steaming: The leaf is exposed to high-temperature steam (around 100°C) for 20–60 seconds. Steam penetrates quickly and uniformly, inactivating enzymes rapidly without the Maillard browning that pan-firing produces. The result retains more of the fresh, grassy, marine (nori/seaweed) character of the leaf and preserves more chlorophyll — producing the vivid green colour and vegetal, umami-rich character of Japanese greens.
Temperature and timing:
Both the temperature and duration of kill-green must be precisely controlled:
- Insufficient heat/time: enzymes survive, partial oxidation continues, producing unwanted browning and loss of green character — the spinachy or dull-green defect
- Excessive heat/time: leaf scorches, aromatic compounds are damaged, and bakey or harsh notes develop — a manufacturing defect analogous to bakey in black tea
Common Misconceptions
“All green teas are processed the same way.”
The choice of pan-firing versus steaming, and the specific temperature and duration parameters, produces dramatically different flavour profiles. Chinese and Japanese green teas differ largely because of kill-green method, not just cultivar or origin.
“Kill-green means the tea is ‘dead.’”
The “killing” in kill-green refers to inactivating the oxidative enzymes — not the plant, and not the complex flavour compounds. The step preserves the living character of the fresh leaf in the dried tea.
Social Media Sentiment
- r/tea: Kill-green / sha qing / fixed green is frequently explained in posts comparing Chinese and Japanese green teas — it’s often the first key distinction that experienced members explain to new tea drinkers wondering why their Chinese green tastes different from their Japanese green.
- Tea YouTube: Kill-green method is a central topic in green tea production videos; the visual of leaf being pan-fired in a wok or tumbling through a steam chamber is a popular educational moment.
Last updated: 2026-05
Related Terms
Research
- Engelhardt, U.H. (2013). Chemistry of tea. In Comprehensive Natural Products II. Elsevier.
Summary: Describes the enzymatic oxidation pathway in tea leaf and the chemistry of enzyme inactivation through heat, explaining at a molecular level what kill-green achieves and why it determines the flavour of green tea.
- Zhu, Y., et al. (2018). Effects of different kill-green methods on the chemical and sensory qualities of green tea. Journal of the Science of Food and Agriculture, 98(8), 3112–3122.
Summary: Compares pan-firing and steaming kill-green methods for their effects on green tea chemistry and sensory character, quantifying the differences in aroma compound profiles, colour, and polyphenol content that result from each method.