Oolong tea is one of the most fascinating types of tea in the world. While green tea is barely oxidized and black tea is almost completely oxidized, oolong falls right in between. This intermediate position is what makes it so versatile: depending on the production method, an oolong can taste fresh and floral or deep, toasty, and complex.
What makes oolong unique is its degree of oxidation —often referred to as the “degree of fermentation.” Although from a scientific perspective the term “oxidation” is used, the term “degree of fermentation” has become established in the tea world to this day.
But what do the different grades actually mean, and how do they affect the taste, aroma, and character of the tea?
What is oolong tea?
Like green, black, and white tea, oolong tea comes from the Camellia sinensis plant. The difference lies not in the plant itself, but in the processing that takes place after harvest.
After picking, the leaves are:
- wilted
- shaken or rolled
- partially oxidized
- heated to stop oxidation
- then rolled and dried
Controlling the oxidation process results in a wide variety of oolong styles.
Oolong is primarily found in:
- China (Fujian, Guangdong)
- Taiwan
is produced and is considered one of the most technically demanding categories of tea.
What does oxidation mean in the context of tea?
Oxidation begins as soon as the cell structure of the tea leaf is damaged and oxygen reacts with the leaf's constituents.
The following change:
- Color
- Flavor
- Taste
- chemical composition
The longer this process goes on, the more the tide turns.
Comparison of the Main Categories
| Type of tea | Degree of Oxidation |
|---|---|
| Green Tea | 0–5 % |
| White Tea | 5–15 % |
| Oolong Tea | approx. 10–80% |
| Black Tea | 80–100 % |
It is precisely this wide range that makes oolong an exceptionally versatile type of tea.
The Different Stages of Fermentation in Oolong Tea
Lightly oxidized oolong (approx. 10–25%)
In terms of flavor, these oolongs are still relatively similar to green tea.
Typical characteristics:
- light yellow infusion
- floral notes
- fresh, plant-like qualities
- a slight sweetness
- creamy texture
Well-known examples:
- Alishan Oolong
- Jin Xuan (Milk Oolong)
- Baozhong
Many tea drinkers discover their love for oolong through this category, as it seems particularly approachable.
Typical flavors
- Orchid
- Lily of the Valley
- Spring Blossoms
- Butter
- Milk
- fresh grass
Medium-oxidized oolong (approx. 25–50%)
This is where the true world of classic oolong begins.
The freshness of green tea is combined with more body and depth.
Typical characteristics:
- A golden to amber-colored infusion
- balanced sweetness
- more complex aromas
- prolonged reverberation
Well-known examples:
- Traditional Tie Guan Yin
- Dong Ding Oolong
- Some Wuyi oolongs
Typical flavors
- Honey
- ripe fruit
- apricot
- roasted nuts
- Flowers
Many tea connoisseurs consider this category to be the most well-balanced part of the oolong world.
Heavily oxidized oolong (approx. 50–80%)
Heavily oxidized oolongs are already verging on black tea.
The fresh notes recede and are replaced by warmer flavors.
Typical characteristics:
- dark infusion
- athletic build
- intense aroma
- long-lasting effect
Well-known examples:
- Da Hong Pao
- Shui Xian
- Rou Gui
- Oriental Beauty
Typical flavors
- Cocoa
- Dried fruit
- toasted wood
- Caramel
- Spices
- Honey
These teas often have impressive depth and continue to develop over many infusions.
Oxidation and roasting—two different things
A common misconception is to equate oxidation with roasting.
In fact, these are two different processes:
Oxidation
Alter the chemical structure of the leaf through contact with oxygen.
Roasting
This occurs later as a result of heat exposure and adds additional flavor notes.
That's why an oolong can:
- slightly oxidized but heavily roasted
- be heavily oxidized but barely roasted
The combination of these two factors creates the enormous diversity within the oolong category.
Why Oolong Is Considered the “King of Teas”
Many tea masters consider oolong to be the most challenging category of tea.
The reason:
The manufacturing process requires the highest level of precision.
Even small changes in:
- Temperature
- Humidity
- Oxidation time
- Roasting
can significantly alter the character of the tea.
As a result, oolong has a wider range of flavors than many other types of tea.
Conclusion
Oolong tea thrives on its diversity. There are whole worlds of flavor ranging from lightly oxidized, floral varieties to robust, darkly oxidized specialties.
The various stages of fermentation and oxidation play a decisive role in this process:
- Color
- Flavor
- Body
- Aftertaste
It is precisely this flexibility that makes oolong one of the most exciting categories of tea. Anyone who tries the different levels of oxidation will quickly discover that oolong is not just a tea—but a whole world of its own, situated between green tea and black tea.
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