Introduction:Taiwanese oolong tea is known for its light fermentation, but the dark-fermented Dong Ding Oolong showcases a distinctly rich character. This article explores the fermentation process in depth, detailing the differences in aroma and flavor between Phoenix Dan Cong and Dong Ding Oolong, and breaking down how "internal oxidation" and "external oxidation" during deep fermentation work together to create the layered complexity and mellow richness of oolong tea. It also includes insights on how rainfall variations in 2018 affected the flavor profile of the leaves, as well as the background behind the sourcing of two high-altitude specialty oolongs—offering a practical guide to understanding the craftsmanship behind Taiwanese oolong.
Taiwanese oolong tea has long been celebrated for its light fermentation and refreshing floral aromas, but traditional dark-fermented Dong Ding Oolong takes a different path, delivering a bold and layered taste. This article will delve into the differences in fermentation techniques, offering an in-depth comparison of the fundamental flavor profiles of Phoenix Dan Cong and Dong Ding Oolong. It also explains how deep-fermented oolong develops its unique fruity notes and rich mouthfeel through the dual processes of "internal oxidation" and "external oxidation." The article also reflects on the changes in tea characteristics due to reduced rainfall in 2018, and the reasons behind sourcing two distinctive high-altitude oolongs from Alishan and Dongding Mountain, serving as a practical guide to appreciating the craftsmanship and tasting profile of Taiwanese oolong.
We have been sourcing oolong tea from Taiwan for a long time. In 2018, due to significantly lower overall rainfall, the internal compounds of the tea leaves became more concentrated, resulting in a richer and more intense flavor—a change that even pleased local tea makers, many of whom couldn’t hide their smiles. Beyond our regular offerings, we also noticed two special oolongs from Alishan and Dongding Mountain, which exhibited unique aromas and flavors, prompting us to introduce them via pre-order, with the deadline set for September 12th.
Before final blending, selecting the right batches of tea leaves is crucial. This is especially true for dark-fermented types, where the crafting process is complex and flavor development requires careful attention. Take dark-fermented Dong Ding Oolong as an example—this type of tea often features a rich and lingering floral aroma, which is one of its defining characteristics.
When discussing dark-fermented Dong Ding Oolong, it’s impossible to overlook the essence of its traditional craftsmanship. In recent years, light fermentation has become the market mainstream, with many consumers accustomed to the fresh, fruity, and easy-drinking qualities of Taiwanese oolong. The term "fermentation," in tea processing, actually refers to "enzymatic oxidation." Lightly fermented teas, with their lower oxidation levels, retain more of the tea leaf’s original freshness, often resulting in a smooth and approachable taste—hence their widespread popularity.
In contrast, Dong Ding Oolong takes the route of deep fermentation, also referred to as "traditional Dong Ding Oolong." These teas undergo multiple stirrings and longer fermentation periods during production, causing the edges of the leaves to take on a distinct orange-brown hue. This process imparts a rich fruity sweetness to the liquor and delivers a fuller, more complex mouthfeel. However, precisely because this intricate manual handling demands considerable labor and time, there are increasingly fewer tea producers who still focus on making traditional dark-fermented oolong.
Interestingly, the dark-fermented Dong Ding Oolong we’ve introduced this time is of premium grade. Although it falls under the dark-fermented category, it presents a refreshing and pleasant floral aroma, which is quite different from the common perception of dark-fermented teas. Nonetheless, the tea liquor still retains the body and layered richness typical of traditional Dong Ding Oolong, with further details on the formation of this unique flavor profile to be explored in the following sections.
The fermentation mechanism of oolong tea can be divided into two main stages: "internal oxidation" and "external oxidation." Commonly seen lightly fermented Taiwanese oolongs typically only undergo internal oxidation—that is, enzymatic oxidation—while the leaves overall remain green in appearance, often leading them to be mistaken for green tea. The flavor profile of such teas tends to be fresh and is well-suited for those new to oolong.
On the other hand, dark-fermented oolongs such as Dong Ding Oolong, Oriental Beauty, and Phoenix Dan Cong, in addition to undergoing internal oxidation, also go through external oxidation. During this phase, the edges of the leaves gradually turn orange due to oxidation, while the liquor gives off pronounced fruity aromas and offers a fuller mouthfeel. Industry insiders often describe internal oxidation as "working inside the body" (行腹內), and external oxidation as "working on the surface" (行出皮).
One noteworthy phenomenon is that if a tea leaf only undergoes internal oxidation and remains green in appearance, no matter how intense that internal oxidation is, the resulting liquor will usually still feature floral notes as the dominant aroma. However, once the edges of the leaf begin to show an orange-red hue, it indicates that external oxidation has begun, shifting the aroma profile toward fruity tones. The location where this oxidation reaction occurs depends on various factors, including stirring frequency, withering time, moisture content of the leaves, relative humidity, and ambient temperature.
During the production of dark-fermented Dong Ding Oolong, tea makers typically maintain strict control over indoor temperature and humidity, sometimes even utilizing air conditioning systems to fine-tune environmental conditions. The goal is to slow down the fermentation rate, allowing internal oxidation to proceed fully and accumulate a richer array of aromatic precursors. This commitment to craftsmanship results in a final liquor that not only boasts intense fruity aromas but also surprising floral freshness, along with a mellow depth reminiscent of wine—delivering an unprecedented sensory experience to tea drinkers.
The above content is compiled by CoffeeHunters, a coffee news website.
