Steaming (Japanese fixation)
Fixation by live steam rather than dry heat — the choice that separates Japanese green tea from Chinese.
The categories this step defines
In tea, processing is not a modifier applied to a category — it is what creates the category. These are the types that exist because this step exists.
- Green tea — Kill-green (fixation) applied before meaningful oxidation can develop.
What it is
Freshly plucked leaf is passed through a steaming chamber for a matter of seconds. The steam denatures the oxidation enzymes without ever bringing the leaf into contact with hot metal, so nothing is toasted and the leaf keeps a vivid green colour. Steam duration is itself a style axis: a short steam (asamushi) leaves needle-like leaf and a clear, delicate cup, while a long steam (fukamushi) breaks the leaf down, giving a cloudy, deep green liquor with a much heavier body. Almost all Japanese green tea is fixed this way; almost no Chinese green tea is.
Also transliterated as: mushi, mushi-sei.
What it does to the leaf
Denatures polyphenol oxidase using saturated steam, arresting oxidation without applying dry contact heat to the leaf surface.
What it does to the cup
Preserves marine, seaweed and umami character and a vivid green colour; contributes no toasted or nutty notes of its own.
Variants that matter
Ways this step is carried out that produce genuinely different results, rather than regional names for the same thing.
- Asamushi (light steam)
- Roughly 30 seconds. Leaf stays intact and needle-like; the cup is clear, delicate and aromatic.
- Chumushi (medium steam)
- The common middle setting for everyday sencha.
- Fukamushi (deep steam)
- Up to two minutes. The leaf breaks down considerably, giving a cloudy, dark green, full-bodied cup with less aroma and more weight.
Where this gets misdescribed
Cloudiness in a deep-steamed Japanese green tea is regularly read as a fault or as poor filtering. It is the intended result of the processing, and the fine particles carry much of the body the style is chosen for.
Other steps at the Fixation stage
- Drum fixation — Kill-green in a heated rotating cylinder that leaf passes through continuously, which is how most Chinese green tea is now fixed.
- Kill-green (fixation) — Heating the leaf to stop oxidation — the step that makes green tea green.
- Pan-firing (Chinese fixation) — Fixation by direct contact with a heated wok or drum, which halts oxidation and toasts the leaf at the same time.
- Spreading and cooling (tan liang) — Getting the heat out of the leaf immediately after a hot step, because heat that stays in the leaf keeps cooking it after the operator has stopped.
Teas that go through this step
- Aracha
- Asamushi sencha
- Cheongtaejeon
- Chumushi sencha
- Enshi Yu Lu
- Fukamushicha
- Goishicha
- Guricha
- Gyokuro
- Kagoshima sencha
- Karigane
- Konacha
- Kuki hojicha
- Kyobancha
- Matcha
- Matcha koicha grade
- Matcha usucha grade
- Matcha-iri genmaicha
- Mecha
- Miang
- Mizudashi sencha
- Sayama sencha
- Sencha
- Shizuoka sencha
- Tencha
- Uji sencha
- Yame gyokuro
- Yu Lu supreme grade
Guides covering this step
- Why green tea tastes grassy — Because the fixation step preserves compounds that oxidation would otherwise transform — and because in Japanese tea, steaming preserves a different set of them than pan-firing does.
- Exploring Japanese tea styles — Almost entirely green tea, almost entirely steamed, and organised around three variables: how long the leaf was steamed, whether the bushes were shaded, and which part of the plant you are drinking.
- Steam or pan: the fork that split green tea in two — Japanese and Chinese green teas taste categorically different, and the reason is not the plant, the place or the picking. It is that one tradition stops oxidation with steam and the other stops it with hot metal.
- Firing, roasting and baking: what heat makes that was not there before — Heat is applied to tea at several points for several different reasons, and only some of them are about drying. The reactions between sugars and amino acids generate an entirely new set of aromas, which is why a roasted tea is not a darker version of an unroasted one.
Sources
- TeaHQ editorial synthesis — TeaHQ
This page is TeaHQ’s own synthesis of well-attested production practice. No external technical document stands behind it, so it describes what producers do rather than asserting measured process parameters.
Written comparisons
Where TeaHQ has set this step against something it is routinely confused with, and argued the differences out in full.
- Steaming to fix leaf vs steaming to soften a cake — The same word, the same equipment in principle, applied at opposite ends of a tea's life for opposite purposes. One stops the leaf changing; the other prepares an already-finished tea to be reshaped.
- Steaming vs pan-firing as kill-green — Both steps do the same job — denaturing the enzymes that would otherwise brown the leaf — and they leave completely different signatures while doing it. This one decision, taken in the first minutes after plucking, is most of why Japanese and Chinese green teas taste unrelated despite sharing a category.