At first glance, the idea seems strange.

When making green tea, we generally seek to preserve the leaf's vegetal expression and color as much as possible.

So why do some producers do exactly the opposite?

Why wrap, cover, pile up or deliberately keep leaves that are still warm and moist?

Why accept that they lose some of their green?

Because, in yellow tea, this change is not an accident.

It is precisely the intended goal.

This step is often referred to by the Chinese term men huang, which is frequently translated as "sealed yellowing".

1. Yellow tea begins almost like green tea

The starting point is important.

Yellow tea and green tea can share several similar steps at the beginning of their transformation.

After harvest, the leaves undergo, among other things, a heating process intended to greatly reduce the enzymatic activity responsible for much of the oxidation.

This is the principle of fixation, which we have already explored in Tsuru n°038 — Why are tea leaves heated?

But then, the path diverges.

Instead of immediately proceeding to conventional drying, some leaves intended for yellow tea go through an additional phase.

They are kept in a warm and moist environment.

2. What is men huang?

Men huang is not an identical process for all yellow teas.

Depending on the region, style and producer, the leaves may be:

• wrapped in paper or a suitable material;
• piled up;
• kept covered;
• reheated and then rested;
• subjected to several cycles of yellowing and drying.

The general principle remains the same, however: retain enough heat and moisture to allow the chemical composition of the leaf to continue to evolve.

3. Why does the leaf lose its green?!--nl-->

A fresh leaf appears green mainly because of its chlorophylls.

However, these pigments are not perfectly stable.

Heat, humidity and time can promote their degradation or transformation.

During yellowing, this evolution helps to gradually fade the green of the leaf.

The result can range from yellow to yellow-green or golden tones.

Research on several yellow teas confirms that the degradation of chlorophylls plays an important role in the formation of their characteristic color.

4. What changes in the polyphenols

Color is only part of the phenomenon.

Polyphenols, including catechins, also change during this phase.

Studies have notably observed a decrease in certain gallic catechins and a change in the ratio between polyphenols and amino acids during yellowing.

These changes contribute to the final taste sensation.

They can help reduce the very pronounced vegetal impression and make the cup smoother or rounder.

But caution is needed: not all yellow teas undergo exactly the same chemical transformation.

The raw material, cultivar, temperature, humidity and duration all play a role.

5. Yellowing also transforms the aromas

The most fascinating change may not be visible.

It is olfactory.

During sealed yellowing, the profile of volatile compounds changes significantly.

Work carried out on Pingyang Huangtang has shown that the duration of yellowing clearly changes the aromatic composition, with an evolution of several alcohols and aldehydes associated with floral, fruity or sweet perceptions.

The leaf gradually loses some of its very green or grassy character.

It can gain in aromatic smoothness, roundness and sometimes more mature notes.

6. Why not simply let it oxidize?!--nl-->

Because it is not the same logic.

In black tea, enzymatic oxidation is a central step in the transformation.

In yellow tea, fixation has already greatly reduced this enzymatic activity.

Yellowing then takes place under particular conditions of heat and humidity.

Thermal, non-enzymatic oxidative, hydrolytic and other chemical transformations can then contribute to the formation of the final profile.

This is why reducing yellow tea to a "slightly oxidized green tea" is too simplistic.

7. Fermentation or no fermentation?!--nl-->

The vocabulary here is tricky.

Some publications and books use the term "light fermentation" to refer to yellow tea.

But the word fermentation can be confusing, especially if it is associated with microbial activity comparable to that of some dark teas.

For yellow tea, it is often more accurate to speak of controlled yellowing under heat and humidity.

This avoids giving the impression that microorganisms are necessarily at the heart of the process.

8. Is time really important?!--nl-->

Very.

Yellowing that is too short can leave a profile that is still very close to that of a green tea.

Yellowing that is too long can, on the contrary, lead to a color that is too dark or to less pleasant notes.

Experimental studies clearly show that duration, temperature and humidity strongly influence the final quality.

The producer must therefore find a balance.

They are not trying to push yellowing to the maximum.

They are trying to stop it at the right time.

9. Why does yellow tea often seem smoother?!--nl-->

This smoothness does not come from an addition.

It results from the transformation of the material already present in the leaf.

The relative decrease in some more astringent compounds, the evolution of polyphenols, the transformation of pigments and the development of new aromatic compounds can together reduce the aggressive vegetal impression.

The result can be a cup that is more supple, rounder, and sometimes slightly sweet in its perception.

But again, this depends heavily on the tea being considered.

10. Are all yellow teas made the same way?!--nl-->

No.

There are several regional styles and several methods.

Some are made from fine buds.

Others use more developed leaves.

The sequence between fixation, yellowing, drying and possible intermediate cycles can also vary.

The term "yellow tea" therefore refers to a family of manufacturing, but not a single recipe.

11. Why does this family remain so rare?!--nl-->

Yellow tea remains much less widespread than green tea or black tea.

Its manufacturing can require more time, monitoring and expertise.

Yellowing is delicate to manage.

Humidity, temperature, duration and ventilation must be managed.

A deviation can quickly change the result.

This is one of the reasons why some productions remain limited or highly localized.

12. Does yellower mean better?!--nl-->

No.

A more intense color is not an automatic measure of quality.

Yellowing that is too advanced can even deteriorate the desired profile.

Quality depends on the overall balance:

• raw material;
• quality of fixation;
• humidity management;
• temperature;
• duration;
• final drying;
• aromatic cleanliness;
• balance in the cup.

Color is therefore an indicator.

Not a verdict.

13. A transformation crafted in the middle ground

Yellow tea is fascinating because it is located in a very subtle territory.

It seeks neither to remain completely faithful to the vegetal profile of a green tea, nor to develop an advanced oxidation like a black tea.

It explores a middle ground.

The leaf is first stabilized.

Then it is deliberately kept in conditions that transform it further.

It is precisely this apparent contradiction that creates its identity.

What to remember

• Yellow tea has a specific step of deliberate yellowing.
• This step is often called men huang.
• It takes place under controlled heat and humidity.
• Chlorophylls partially degrade.
• Polyphenols and certain catechins change.
• The aromatic profile transforms.
• The tea can lose some of its vegetal character and gain smoothness.
• Yellowing is not identical to the oxidation of a black tea.
• Duration and humidity must be mastered.
• A yellow tea is not a failed green tea.