Black Tea: The Oxidation / Fermentation

Black tea is the most frequently drunk tea in Europe. In China it is called "red tea" after the infusion color. 

Black Tea is oxidized

Black tea is an oxidized tea, not a fermented tea, as is often written.
After picking and withering the fresh tea is "rolled"in the tea factory, what opens the leaf. So it can react with oxygen, what is chemically known as oxidation.
No microorganisms are involved that would be necessary for a fermentation.

Typical fermentation products


Bacteria, fungi or other microorganisms carry out an enzymatic / fermentative processing.

Oxidation makes Black Tea more durable

The oxidation of black tea converts the sensitive catechins, which makes the tea more durable. It is therefore better suited for longer transport, and it can also be stored. A well-preserved black tea still has its full aroma two years after harvesting. It is important to keep it dry, cool and protected from light.

The just mentioned catechins in the green tea quickly give the infusion a bitter note, which does not suit everyone. During oxidation, the catechins are converted into theaflavin and thearubigen, resulting in a more moderate infusion. Theaflavin and thearubigen also give the black tea its dark colour.

Pu-Erh is fermented

It is also important to differentiate between oxidation and fermentation in order to distinguish between black tea and Pu-Erh.
Pu-Erh is refined by microorganisms, and so it is fermented.
Black tea is oxidized
Pu-Erh is fermented
Green tea is neither oxidized nor fermented

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