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Lesson #4. The degree of fermentation of the tea leaf

All division by types (green, white, red, oolong, shu and sheng pu’er) originates from tea production technology. We will talk about technology later on, and today let us focus on the degree of tea leaf fermentation as it is important for understanding of the brewing process and tea ware used for tea flavor delivery. Bear in mind that when it comes to tea, first of all under fermentation we mean enzymatic oxidation process.

Fermentation

Non-fermented.
The lowest percentage of fermented tea sap.
Green leaf, clear brew.

Fully-fermented.
The highest degree of fermented tea sap.
Dark-brown leaf, dark brew.

And so, while processed the tea leaf brakes exuding the tea sap, which in contact with air oxygenates and ferments, changes its chemical composition and respectively the properties and the flavor of the leaf. The fermentation may be either controlled or uncontrolled. When controlled, the tea sap is fermented deliberately for the delivery of leaf flavor properties. Uncontrolled implies that the sap exudes and oxygenates as it is impossible to prevent it in the production process. In other words it is not desired but happens anyway.

The degree of fermentation of the tea leaf

Tea type Fermentation % of ferm.  
Green tea Non-fermented 1-5 Uncontrolled fermentation
Yellow tea Light-fermented 9 Uncontrolled fermentation
White tea Light-fermented 11-15 Uncontrolled fermentation
Red tea Fully-fermented 90-100 Controlled fermentation
North Fujian Oolongs Semi-fermented 60-80 Controlled fermentation
South Fujian Oolongs Semi-fermented 30-50 Controlled fermentation
Guangdong Oolongs Semi-fermented 25-50 Controlled fermentation
Taiwan Oolongs Semi-fermented 15-80 Controlled fermentation
Shu pu’er Postfermented 100 Controlled fermentation
New sheng pu’er Postfermented 15 Controlled fermentation
Mature sheng pu’er Postfermented 90 Uncontrolled fermentation

How does it affect brewing? The higher the degree of fermentation, the higher is the temperature of brewing. With oxidation over 10%, the temperature of water should be 90°C , if over 20% may be easily brewed in 100°C water. The higher fermentation percent requires brewing vessel with higher heat capacity.

Fermentation degree
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