Tea Fermentation: Understanding the Different Types of Tea

Tea is one of the most widely consumed beverages in the world, and many of its varieties come from the same plant – Camellia Sinensis. However, the different types of tea are a result of variations in the tea manufacturing process, including fermentation.

Understanding Tea Fermentation

Fermentation is a critical step in the tea manufacturing process that determines the degree of enzymatic oxidation the tea leaves undergo before drying. The oxidation process can be halted by roasting or steaming the leaves before they dry out completely. During fermentation, the deep green tea leaves transform into a reddish-brown color, with darker shades resulting from longer fermentation periods. Depending on the roasting and fermentation degree, the fragrance can range from floral to fruity and malty.

Classifying Teas Based on Fermentation

Teas can be classified based on their degree of fermentation, which includes:

Non and light-fermented teas

These include white and some green teas with an oxidation state of up to 10%, which have not undergone the fermentation process or have undergone weak fermentation. These teas retain their natural color and properties and are considered a healing drink with a fresh, natural aroma.

Semi-fermented teas

These are teas that undergo 10% to 80% fermentation and are classified into three categories based on their levels of fermentation:

  • Light (10% – 20%): Includes Jasmine Tea (Pouchong scented with Jasmine petals), Pouchong Tea, and Mei Shan Full Aroma Oolong, with a light golden color and full aroma, clarity, and flavor.
  • Medium (20% – 50%): Includes most Oolongs, Dong-Ding (Tung-Ting) Oolong, and Tieguanyin, with light green-brown color, full flavor, and sweet taste and aftertaste.
  • Heavy (50% – 80%): Includes Oriental Beauty Oolong Tea (Dongfang Meiren) and Red Oolong Tea (Hong wu long) from Hsinchu, with red-orange color and fruity aroma and taste.

Fully-fermented teas

These are teas that have undergone complete fermentation and include black teas, with a dark red color and sweet aroma of malt sugar.

Post-fermented teas

These are teas that undergo fermentation, then have the process stopped and later fermented again, such as Pu-Erh Tea, which has a specific aroma, color, and taste dependent on the degree of processing.

Fermentation Process

Tea leaves are placed in large, cool, moist, and darkened rooms, where they are laid out on flat surfaces with an even layer of about 10 cm. Aluminum or wood is often used to avoid chemical reactions between the tea leaf juice and the surface. The ideal combination for fermentation is a low temperature of about 15°C and high humidity of about 90%. Fermentation can last from 45 minutes to several hours.


Tea fermentation is a critical process that determines the type of tea and its unique aroma, color, and taste. Understanding the different types of teas and their levels of fermentation is essential for selecting the ideal tea to suit individual preferences and health needs.

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