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# Fixation, Oxidation, Fermentation — three words that change your cup of tea
- URL: https://www.storiesbehindgoods.com/fixation-oxidation-fermentation-three-words-that-change-your-cup-of-tea/
- Published: 2026-09-28T05:59:55.000Z
- Updated: 2026-09-28T05:59:55.000Z
- Author: MingHongKong

In the last weeks we looked at tea categories and at how personal palate shapes what people notice in the cup.

This week I want to make three processing terms clearer — because they explain why some “dark” teas behave so differently.

**1) Fixation (殺青）**  
  
Fixation uses heat to stop the enzymes in **freshly picked leaves**.  
  
Once stopped, the leaf largely keeps a greener, less transformed character.

**2) Oxidation 氧化 (Black tea 紅茶)**

Black tea starts from fresh leaves.  
The leaf’s own enzymes react with air.  
Moisture and sugars in the fresh leaf support this transformation.

During oxidation, catechins are converted into larger compounds such as theaflavins and thearubigins.  
This changes both colour and mouthfeel.  
Because this happens on the fresh leaf, more of the lighter aromatic character can remain than in darker, microbially transformed teas.

Result: a fuller, more aromatic cup with a different polyphenol profile from green tea or dark tea.

Simple picture: a cut apple turning brown in air.

---

**3) Fermentation 發酵 (Dark tea 黑茶 / ripe Pu-erh 熟普)**

Dark tea is different.  
Ripe Pu-erh, for example, is not mainly transformed from fresh leaves in the same way.

It is made from already sun-dried green tea leaves (raw Pu-erh).  
Water is added, and microbial activity transforms the dried leaf further.

Microbes break down parts of the leaf material, which can increase smoother, rounder soluble components and reduce the brighter, more astringent edge common in less transformed teas.

Result: a darker, heavier liquor, usually less focused on bright top notes, with a different body and finish from black tea.

Simple picture: apple cider or pickle — microbes transforming the material — rather than a cut apple browning by itself.

**Why this matters in practice**

- Aroma and body are different
- Brewing tolerance can differ
- Staff should not explain them as the same “dark tea”
- Serious drinkers can taste with clearer expectation

**Why this matters**  
  
Black tea and dark tea are often mixed up in daily language.  
  
But one is mainly an enzymatic oxidation path, while the other involves microbial fermentation.  
  
That difference affects aroma, body, brewing behaviour, and how staff should explain the tea.

If you want a short visual:  
  
→ Green fixation vs black oxidation (90 seconds): [https://youtu.be/05dxiWXuOwc](https://youtu.be/05dxiWXuOwc?ref=storiesbehindgoods.com)

Optional longer reading:  
  
→ Why people mix up black tea and dark tea: [\[Medium link\]](https://medium.com/@hkfairgoods/why-people-mix-up-black-tea-and-dark-tea-0e4ea0556801?sharedUserId=hkfairgoods&ref=storiesbehindgoods.com)

Warmly,

Ming

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