Lesson 8/4 : Oolong Tea Processing

My Little Tea School - The ABC of TEA : Lesson 8.4. - Oolong Tea Processing

What is Oolong Tea?

The second of the 6 Chinese tea processing categories that we got to know in Lessons 8.1 and 8.2 is the Oolong tea. The most discerning feature of the teas of this category is the part oxidation of the tea leaves during their processing.

The method is considered the most complex of the 6 tea processing categories. This is partly because “partial oxidation” covers the entire range of oxidation levels between 10% and 90% percent. Then, varying processing steps follow the oxidation stop depending on variety and origin, for example one or more roasts. Accordingly, Oolong teas can be very diverse – and the same applies to their taste!

There are a quite some myths and legends trailing the origins of oolong tea processing. Since the veracity of these – all too often quoted – legends ultimately blurs in the fog of ancient times, we will restrain our coverage here to the historically evident.

4 types of Oolong tea, one from every classic origin region of Oolong teas : Da Hong Pao Oolong from Wuyishan (Fujian), Jin Xuan Oolong from Taiwan, Tie Guan Yin Oolong from Anxi (Fujian) and Mi Lan Xiang Dancong Oolong tea from Fenghuanshan Phoenix Mountain (Guangdong)
4 origins / 4 types of Oolong tea

History of Oolong Tea Processing

The history of partial oxidation of tea leaves dates back to the time of the Song dynasty (960-1279 AD). At that time, the imperial court operated a tea garden in Beiyuan, Fujian, about 120 km northeast of Wuyishan. The “dragon and phoenix” teas of the tea garden, contemporarily pressed in flat form, were for a long time one of the most important tribute teas of imperial China. However, at the time of the Tang dynasty (618-907), the imperial court’s preferences shifted in favor of loose leaf tea, which as a result increasingly displaced the pressed tea.

In Beiyuan, too, they started producing loose “dragon & phoenix” teas. While the Beiyuan tea garden saw its decline in the subsequent period, the partial oxidation method soon found imitation in adjacent regions. Whether the term “oolong tea” was finally invented in Wuyishan or Anxi, the two tea regions are still arguing about today. In any case, “wu-long” means “black dragon”, which on the one hand indicates the typical appearance of the leaves of Wuyi Oolong teas and on the other hand suggests the reference to Beiyuan tea.

Four Classic Origins of Oolong Tea

Four classic origin regions of Oolong Tea : Wuyishan (Fujian), Anxi (Fujian), Fenghuangshan Phoenix Mountian (Guangdong) and Taiwan
Four classic origin regions of Oolong Tea

From the above course of history finally arise the following 4 classic origin regions of Oolong tea:

In tea producing countries outside of China, the method of oolong tea processing has long met ignorance. However, there are also approaches to this today in Darjeeling, Japan, northern Thailand and Vietnam, for example.

Overview of Processing Steps

Let’s now look at the processing of oolong tea on a step-by-step basis.

Tea Processing : Oolong Tea - Step-by-step overview
Oolong tea processing – step by step
click picture to enlarge
1. Withering

Typically, when processing Oolong tea, the freshly picked tea leaves first wither outdoor in the sun for a few hours. After this follows a second phase of withering inside the shady factory hall. Both with outdoor and indoor withering, it is important that air reaches the tea leaves unhindered, so that the initial oxidation processes can evenly effect. Traditionally, large round bamboo trays commonly find use for this in China.

As with the processing of green tea, the withering initially serves to increase the suppleness of the tea leaves by losing water. Once reaching the degree of suppleness fit for the second processing step, the withering seamlessly passes in the next processing step.

Oolong Tea processing - withering, oxidation, roasting, rolling
Oolong Tea processing – withering, oxidation, roasting, rolling
2. Bruising the leaf surfaces

During indoor wilting, the second processing step sets in, the breaking up of the leaf surfaces. What should be carefully avoided when processing green tea, is essential in oolong tea processing. Through continuous swirling and tumbling of the tea leaves with controlled exertion of force, the leaf structures are broken up without destroying the leaf as a whole.

The tea juices leaking at the break points react with the oxygen from the air. This manifests in an initially reddish color forming around the break lines. In the further course of processing, this discoloration becomes darker, eventually changing to brown, grey and bluish. This has led to the category’s common alternative designation as “blue tea”.

The thus accelerated oxidation processes on parts of the leaf surface are coining the characteristic taste of Oolong teas. As we have seen above, the oxidation in the processing of oolong tea starts already during the withering phase. In order to make processes as uniform as possible, the tea master will re-whirl the leaves from time to time during the oxidation phase. Through continuous sensory examination (appearance, smell, haptics) he will finally decide when the desirable degree of oxidation is reached.

Tie Luo Han Wuyi Oolong
Tie Luo Han Wuyi Oolong
3. Partial Oxidation

Regional examples are obvious. Anxi, for example, in ancient times tended to higher oxidation levels of Tie Guan Yin Oolong. Today, however, the majority of Tie Guan Yin on the market shows a very low level of oxidation. The corresponding development in the processing of Tie Guan Yin Oolong ultimately owes to the – both actual and anticipated – preferences of the end customer. In contrast, oxidation levels in the upper third of the scale have always been common for Wuyi and Dancong Oolong teas. And although Taiwan covers the whole range with its variety of different oolong teas, also here specific types of tea will usually show a characteristic level of oxidation.

Dancong Oolong, Fenghuangshan,
Dancong Oolong Tea, Fenghuangshan, Guangdong
4. Oxidation Stop (Fixation)

After reaching the desired degree of oxidation follows the stop of the oxidation process (Chinese 殺青 sha-qing). Initially, the heat causes degeneration of the enzymes in the tea leaf. As a result, they lose their ability to react, so that the enzymatic reactions of the juices in the tea leaf come to a halt. The degree of oxidation is now virtually “fixated”, which is why this processing step is often referred to as “fixation”.

The most ancient form of fixation is heating the tea leaves in a wok pan over charcoal fire. Today, however, this method is increasingly displaced by modern ovens.

5. Rolling

The shape that the tea leaves typically receive ith rolling also varies with the region of origin – and from variety to variety. Thus Oolong teas from Wuyishan and Guangdong usually come as an open-rolled, slightly curly leaf. In contrast, Tie Guan Yin Oolong teas from Anxi and many Taiwanese oolong teas usually come in ball shape.

For rolling, one first tightly wraps the tea leaves in a cloth to form a solid bale. This bale is then – manually or mechanically – worked and kneaded until the tea leaves take on the desired shape.

However, the rolling of the tea leaves does not only serve aesthetic purposes. Rather, it is an extremely sensitive process that has significant impact on the taste of the finished tea. In fact, it is a question of permanently removing remaining cell walls and structures in the tea leaf and promoting an even distribution of the juices in the tea leaf. In the subsequent roasting or final drying step, the resulting shape receives permanent consolidation.

Oriental Beauty Oolong (Taiwan)
Oriental Beauty Oolong (Taiwan)
Roasting / Drying

In the course of the previous processing steps, the tea leaves have continuously lost moisture. In the interest of good storability and the lasting preservation of taste and aroma, it is necessary that no more than an picayune residual moisture remains in the leaves. Therefore, at the end of the processing (not only) of Oolong tea is a final drying. There are two basic types: roast drying and air drying.

Whether an oolong tea is roasted, how exactly and how often, varies from region to region and from type to type. For example, roasting over charcoal fire is a characteristic feature of both Wuyi-oolongs and Dancong-oolong teas (Guangdong). Actually, it strongly characterizes the typical taste of these teas. In this case, roasting and rolling in pratice alternate several times during processing. In Anxi, both types are common, roasted and unroasted Oolong teas. While roasting there used to be typical of Tie Guan Yin teas, the air-dried version is more prevalent in the modern, low oxidation type of TGY . And in Taiwan, too, there are all variations of roasted and air-dried Oolong teas existing today.

One more thing, on my own account…

Do you like this article? Support the maintenance and further development of “My Little Tea School – The ABC of TEA” through your shopping at

Siam Tea Shop - Finest Artisan and Specialty Teas
from all over the world
Finest Artisan and Specialty Teas
from all over the world