As someone deeply immersed in tea chemistry, I understand the common questions many tea enthusiasts have - questions that may seem simple but are essential for tea lovers. For example, people often ask, "What is tea fermentation?" "Is black tea fermented?" and "What makes the six major tea types different?"

In this article, we'll provide a detailed explanation of the fermentation processes involved in each of the six main types of Chinese tea.

Is Black Tea Fermented?

Yes, black tea is considered a fermented tea. In traditional Chinese tea classification, black tea is usually described as a fully fermented tea. However, "fermentation" here is not the same as microbial fermentation in yogurt, cheese, pickles, or soy sauce.

In black tea production, "fermentation" mainly refers to enzymatic oxidation. After fresh leaves are withered and rolled, the cell structure of the tea leaves is broken. Polyphenols inside the leaves then react with enzymes and oxygen. This oxidation process gradually darkens the tea leaves and creates the richer aroma, redder liquor, and smoother sweet taste associated with black tea.

If you want to compare black tea with green tea more directly, see our guide on black tea vs green tea.

What Does Tea Fermentation Really Mean?

In traditional tea-making processes, "fermentation" refers to a key step that creates the distinctive color, aroma, and flavor in teas like black tea. Proper fermentation enhances the tea's taste and aroma. Freshly picked tea leaves undergo steps like withering, rolling, fermentation, and drying. Different types of tea vary in how they are fermented, and based on the degree of fermentation, we categorize teas into six main types.

However, it is important to note that tea fermentation differs from the typical fermentation we associate with foods like yogurt, cheese, and soy sauce. Traditional food fermentation usually involves microbes breaking down organic matter to produce new compounds.

Tea "fermentation," in contrast, is more accurately described as a biochemical oxidation process, catalyzed by enzymes naturally present in the tea leaves. Inside tea leaves, catechins are located in the cell fluid, while oxidase enzymes are stored in the cell walls. When the cell walls are broken through processing like rolling, the enzymes and catechins interact with oxygen, initiating oxidation. This controlled oxidation creates different flavors and tea colors, ultimately distinguishing fully fermented, semi-fermented, and lightly fermented teas.

Dark tea is different. In dark tea and ripe Pu-erh, microbial post-fermentation also plays an important role.

How Fermented Is Each Type of Chinese Tea?

Non-Fermented Teas: Green Tea

Green tea is a non-fermented tea, which preserves its fresh aroma and flavor, resulting in a bright, greenish infusion. Popular Chinese green teas include West Lake Dragon Well, Bi Luo Chun, and Huangshan Maofeng. It is best not to drink strong green tea on an empty stomach if you are sensitive, because its high polyphenol content may feel irritating.

Lightly Fermented Teas: Yellow Tea and White Tea

Yellow and white teas are lightly fermented or lightly oxidized. Yellow tea undergoes a unique "yellowing" step during drying, allowing slight oxidation of polyphenols and chlorophyll. Famous yellow teas include Junshan Silver Needle and Mengding Yellow Tea.

White tea is processed by simple withering and drying, preserving the leaf's natural appearance and delicate white hairs. It produces a clear, pale yellow tea with a light, sweet taste, often enjoyed by those new to tea. Well-known white teas include Fuding White Tea, Bai Mudan, and Shou Mei.

Semi-Fermented Teas: Oolong Tea

Oolong tea is a semi-fermented or partially oxidized tea, known for its captivating natural aroma without added flavors. The oxidation level in oolong can range widely. Key regions for oolong tea include Fujian, Guangdong, and Taiwan, producing renowned varieties like Tieguanyin and Phoenix Dan Cong.

Fully Fermented Teas: Black Tea

Black tea is fully fermented in traditional Chinese tea terminology, yielding a rich red infusion. Originating in Wuyi Mountain's Tongmuguan area, black tea production involves withering, rolling, oxidation, and drying. Black tea is often perceived as smoother and warmer than green tea, making it suitable for many daily tea drinkers. Major black tea-producing regions include Fujian, Yunnan, and Anhui, with popular varieties like Jin Jun Mei and Lapsang Souchong.

Post-Fermented Teas: Dark Tea

Dark tea undergoes post-fermentation, where leaves are piled together under specific humidity and temperature, enabling microbial activity. This secondary fermentation creates dark tea's characteristic smooth, mellow flavor. Regions like Xinjiang and Inner Mongolia traditionally favor dark tea, often enjoying it after heavy meals. Notable dark teas include ripe Pu'er tea and Liu Bao tea.

How to Choose Tea by Fermentation Level

Fermentation level is an important reference when choosing tea. It affects the tea liquor color, aroma, taste, and the way the tea feels on the stomach. In general, the lower the fermentation level, the fresher and more direct the tea may taste, but it may also feel more stimulating. The higher the fermentation level, the thicker, smoother, and more mature the tea usually tastes.

What Tea Should You Choose If Your Stomach Is Sensitive?

If your stomach is sensitive, it is usually better to choose teas with a higher fermentation or oxidation level. Black tea, roasted oolong tea, and ripe Pu-erh tea often feel smoother than strong green tea or young raw Pu-erh tea.

This is not a medical rule, and everyone's body is different. But in Chinese tea-drinking experience, highly fermented or post-fermented teas are often preferred for daily drinking by people who dislike the sharpness of green tea.

If you want a mellow post-fermented tea, start with ripe Pu-erh tea.

Tea Fermentation Summary

To simplify, tea is categorized into six main types based on fermentation level: green tea (non-fermented), white and yellow teas (lightly fermented), oolong tea (semi-fermented), black tea (fully fermented), and dark tea (post-fermented).

Different fermentation levels affect the taste and aroma of tea. Low-fermentation teas such as green tea are fresh and crisp. Highly fermented teas such as black tea and dark tea are thicker, smoother, and more mellow. Oolong tea sits between the two, combining floral aroma and richer taste. Understanding fermentation level helps you choose tea according to your flavor preference and stomach comfort.

SEE MORE ABOUT CHINESE LOOSE LEAF TEA

If you are a beginner about Chinese tea:
Basic-Guide-to-Chinese-Tea

If you have questions about selecting tea:
Learn-more-about-chinese-tea

If you have questions about the benefits of tea:
Health-benefits-of-chinese-tea

If you have questions about brewing tea:
How-to-brew-loose-leaf-tea