At first glance, the two techniques seem to pursue the same goal.

And that is true.

In both cases, the goal is to heat the leaves quickly to significantly reduce the activity of the enzymes responsible for much of the oxidation.

This is what is known as fixing.

Without this step, a green tea would continue to change rapidly after harvest.

Its color, aromas, and composition would change profoundly.

But while the goal is the same, the way of achieving it greatly affects the result.

1. Fixing: stopping a transformation before it really begins

When leaves are harvested, they are still biologically active.

Their cells contain polyphenols and enzymes such as polyphenol oxidase.

If the tissues are damaged and oxygen is present, these elements can react with each other.

The color changes.

The aromas change.

The leaf gradually enters another type of transformation.

In green tea, the producer specifically seeks to limit this change.

They therefore heat the leaves quickly to significantly reduce enzymatic activity.

We detailed this principle in Tsuru n°038 — Why are tea leaves heated?

2. What happens with steam?

In steam fixing, the leaves are exposed to hot water vapor.

The heat quickly penetrates the tissues.

This method very quickly inactivates a large part of the oxidative enzymes.

Studies on green tea production show that steam parameters—duration, flow rate, temperature—directly influence the effectiveness of this inactivation.

Too short a steaming process can leave more enzymatic activity.

Excessive steaming can, on the contrary, alter the texture or aromas.

The process may seem simple.

In reality, it must be extremely precise.

3. Why does steam often produce a more vegetal profile?

Steam heats quickly without creating as much contact with a hot surface.

It therefore limits certain thermal reactions typical of intense dry heating.

The resulting teas can retain more vegetal freshness, sweetness, umami, or notes reminiscent of fresh grass, green vegetables, or sometimes marine impressions.

This does not mean that all steamed teas taste the same.

The cultivar, harvest, steaming duration, rolling, drying, and eventual final roasting greatly change the profile.

But steam often steers the tea toward a fresher, more vegetal expression.

4. Why do the leaves often remain greener?

The color of the leaf depends in part on its chlorophylls.

However, these pigments are sensitive to heat.

Very rapid steam fixing can limit their degradation compared to some longer or more aggressive heating methods.

Studies comparing steamed green tea and dry-heated green tea made from similar raw materials show that steam can retain more chlorophyll.

This contributes to leaves and sometimes infusions that appear greener.

But beware: a very green color is never, on its own, proof of quality.

5. What happens in a wok?

With dry heating, the leaf comes into contact with a hot surface or with very hot air in a drum.

The heat is therefore transferred differently.

It does not merely inactivate the enzymes.

It also gradually participates in the creation of thermal aromas.

Depending on the temperature and duration, notes may appear:

• roasted;
• toasted;
• chestnut;
• hazelnut;
• cereal;
• sometimes slightly caramelized.

These impressions do not come from an added aroma.

They arise from the thermal transformation of the material itself.

6. Does dry heating really create new aromas?

Yes.

The high temperature can cause or accelerate many chemical reactions.

Some aromatic precursors are transformed.

Volatile compounds appear.

Others disappear.

Studies on green teas show that the fixing method plays a major role in forming the final aromatic profile.

Dry-heated teas are notably often associated with more roasted or chestnut notes.

Steamed teas generally remain more associated with fresh and vegetal profiles.

7. What changes in the catechins and amino acids?

Fixing does not only affect aromas.

It also modifies non-volatile constituents.

Studies show that production conditions can influence:

• certain catechins;
• free amino acids;
• soluble sugars;
• chlorophylls;
• caffeine to a lesser extent;
• the overall composition of the infusion.

One study comparing steamed green tea and dry-heated green tea, made from the same batch of fresh leaves, notably observed more free amino acids and soluble sugars in the steamed tea.

These differences can contribute to a smoother, fresher, or rounder sensation.

However, it would be wrong to make an absolute rule of it.

The raw material remains decisive.

8. Japan equals steam and China equals wok?

This is a useful simplification to start with.

But it quickly becomes false if it is turned into an absolute rule.

Steam is particularly associated with Japanese green teas, notably the sencha families.

China widely uses dry heating techniques.

But the boundaries are not watertight.

There are Japanese green teas heated in a pan.

Kamairicha is a well-known example.

Conversely, China has an ancient history of steamed green teas.

We must therefore speak of large dominant traditions.

No universal rules.

9. Is steam a gentler technique?

The word "gentle" can be misleading.

Steam may seem more delicate because it does not expose the leaves to a hot surface.

But the thermal intensity remains significant.

Steam must transmit enough energy to quickly inactivate the enzymes.

Everything comes down to mastery.

Too little heat and the fixing is insufficient.

Too much heat or too long, and the leaf loses part of its finesse.

Steam is therefore not a "gentle" version of the wok.

It is another way of heating.

10. Can you recognize the method solely by taste?

Not always.

But certain clues can guide the tasting.

A steamed tea may evoke:

• fresh grass;
• green vegetables;
• seaweed;
• spinach;
• vegetable broth;
• umami.

A dry-heated tea may more strongly evoke:

• chestnut;
• hazelnut;
• cereals;
• toast;
• hot seeds;
• certain floral or sweet notes.

But none of these markers are exclusive.

Terroir, cultivar, and the rest of the process can easily muddy the waters.

11. And roasting in all this?

We must avoid confusing fixing and roasting.

Fixing occurs very early after harvest.

Its main role is to inactivate the enzymes.

Roasting can occur later in the process to dry, stabilize, or further transform the aromatic profile.

Both steps sometimes use heat.

But their role is not identical.

We have already dedicated a Tsuru to this distinction: Tsuru n°011 — Why are tea leaves dried and roasted?

12. Why does this step change the personality of a tea so much?

Because it occurs at a critical moment.

The leaf has just been harvested.

Its composition is still close to that of living plant matter.

Fixing largely decides the direction the transformation will take.

It stops certain reactions.

It triggers others.

It preserves certain compounds.

It transforms others.

In a few seconds or minutes, it already contributes to writing a large part of the future taste of the tea.

What to remember

• Fixing is used to greatly reduce the activity of oxidative enzymes.
• It can be done notably with steam or dry heat.
• Steam quickly transmits heat to the heart of the leaf.
• It is very widespread in the production of many Japanese green teas.
• Dry heating is very common in many Chinese green teas.
• Steam often favors fresher and more vegetal profiles.
• Dry heating often favors roasted, chestnut, or cereal notes.
• The method influences chlorophylls, amino acids, catechins, and aromatic compounds.
• Japan does not always mean steam, and China does not always mean wok.
• Neither method is inherently superior.