How to Categorize Taiwan Teas by Oxidization?


In this article, you will learn another tip to quickly sort through the variety of Taiwan teas, particularly Oolongs. The tip is to categorize them based on oxidization levels. Oxidization? Never heard of it? And why is it important, or what this categorization can do for you as a tea drinker, even if you do not yet fancy Oolongs? Well, unless you would always prefer to select a tea based on added flavorings and scents, which are more of an industrial add-on than a natural occurrence from within leaves and stems, it may gain you a different perspective on how to appreciate your cuppa.

What Is Oxidization?

Oxidization level can serve as a key benchmark to select teas that meet your personal preference, presumably, you have the experience of how black tea and green tea taste like. Oxidization level is measured by the percentage that catechin is lost during tea processing. Catechin is a type of natural phenol and antioxidant. In the case of green tea, catechin is nearly 100% preserved because tea leaves have gone through very little processing. Hence, it is zero oxidized. On the contrary, catechin is virtually all lost as a result of processing tea leaves into black tea, so the oxidization is nearly 100%. A simpler way to express the relation between oxidization and catechin is like this: Oxidization (%) = 1- catechin (%).

Tea Oxidization from Low to High

In between these two spectrums come Oolong teas. As you may see from the table below, the oxidization levels of Taiwan Oolong teas can range from as light as 8%, to as heavy as 70%. In other words, the taste of Pouchong Oolong is closer to green tea, still high in catechin content but a bit less in astringency and bitterness as green tea may normally has. Bai Hao Oolong is closer to black tea while retaining more catechin. Therefore, if you’re a green tea fan and would like to venture into Oolong, it’s safer to start with light oxidized Oolong and gradually expand to heavier oxidized Oolong. The opposite is recommended for a black tea fan.

Green Tea (0% oxidization): Dragon Well

Oolong Tea:

  • 8-18% oxidization: Pouchong
  • 20-25% oxidization: Alishan, Jin Xuan, Jade, Shan Lin Xi, Da Yu Ling, etc.
  • 30% oxidization: Dongding
  • 40% oxidization: Tieguanying
  • 50-70% oxidization: Bai Hao (Oriental Beauty)

Black Tea (100% oxidization)

Tea Liquor Color from Pale Yellow, Bright Golden, to Amber

Since you have by now learned the oxidization spectrum among Taiwan Oolong teas, you can also visualize the oxidization levels by the color of tea liquor after brewing. In the case of Taiwan Oolongs and black tea, oxidization levels are fairly in line with the liquor color – the lower the oxidization of a tea, the lighter the liquor color (e.g. pale yellow); the higher the oxidization, the darker the liquor color (e.g. bright amber, dark amber).

The after-thought you might have after seeing these colors: does that mean the teas (packed in tea bags particularly) available in the mass markets are mostly produced based on 100% fully oxidized tea leaves because their color after brewing tends to be so dark red or brown? The answer is quite obvious, isn’t it?


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