Have you ever wondered what gives Pu'er tea and Goishicha their unique flavors? The answer lies in the role of microbes in producing these distinct tastes and aromas. Fermented tea, which includes Pu'er tea and Goishicha, is created using a method that utilizes these helpful microorganisms.

Features of fermented tea process

In the world of tea, the term "fermentation" generally refers to oxidative fermentation, which is caused by enzymes. However, the fermentation process used in fermented tea is caused by microbes such as mold and lactic acid bacteria. By fermenting the leaves with these microbes, fermented tea is able to achieve its unique characteristics.

Difference by type of microbes to be used

Fermented tea is made using two main types of microbes: mold and bacteria. Mold, such as kōji-mold, thrives in oxygen-rich environments, while bacteria, like lactic acid bacteria, prefer oxygen-free environments.

Pu'er tea is made using only mold, while Awabancha uses only lactic acid bacteria. Goishicha, on the other hand, undergoes a two-stage fermentation process and uses both mold and lactic acid bacteria.

Fermented tea process

Each type of fermented tea has a unique manufacturing process, which depends on the type of microbe used. Pu'er tea, Awabancha, and Goishicha all have different processes.

Pu’ er tea

Pu'er tea is a type of tea that undergoes fermentation for months or even years with the leaves pickled in Kōji mold. The ripening degree of the tea affects its flavor and health benefits. In some cases, it can take more than ten years to ripen.

The plucked leaves are steamed to deactivate oxidative enzymes in the leaves, a process that is known as oxidase deactivation by steaming.

1. Rolling

The leaves are kneaded while still hot to ensure uniform moisture in the leaves, which helps the tea's ingredients come out easily.

2. Wo doi (Molding)

The next step is adding mold to the leaves and fermenting them under controlled temperature and humidity. The accuracy of this process is crucial as it plays a vital role in determining the tea's quality, flavor, and aroma.

3. Drying

Finally, the hardened leaves are loosened by drying, resulting in the highly sought-after Pu'er tea.


Awabancha is a unique type of tea that is produced through fermentation using indigenous bacteria found in wooden buckets. It is a locally-produced tea that has been passed down through generations in Tokushima Prefecture.

1. Deactivation by boiling

The process of creating delicious Awabancha tea starts with deactivating leaf enzymes through boiling. This prevents oxidative fermentation and suppresses the growth of unwanted bacteria, ensuring a safe and healthy tea.

2. Rolling

Kneading the leaves evenly spreads the moisture and helps release the leaf ingredients, contributing to the flavor and aroma of the tea.

3. Pickling

To begin the process, rolled tea leaves are stuffed into a large bucket with boiled tea soup. The air is then removed by poking the leaves from the top, and the bucket is covered with a wooden lid and a heavy stone. This creates an anaerobic environment in which lactic acid bacteria can begin fermentation. The pickling process typically takes 2-5 weeks.

4. Drying after bucket opening

After fermentation is complete, the leaves are removed from the bucket and sun-dried. The dried leaves are then sorted, and thick stems and other unwanted parts are removed. The resulting tea, known as "Awabancha," is ready for consumption.


"Goishicha" is a type of tea that has been produced in Kōchi Prefecture since the Edo Period. This unique tea undergoes a two-stage fermentation process using both mold and lactic acid bacteria. The same production method has been passed down for generations. The tea also relies on indigenous bacteria that naturally live in a storehouse or straw mat.

1. Deactivation by steaming

Tea leaf picking for Goishicha involves twig clipping instead of leaf plucking. The leaves are then steamed to deactivate oxidative enzymes.

2. Molding

After steaming, the leaves are spread and left for around a week on a straw mat in a molding room where fermentation begins, and lactic acid bacteria grow on the tea leaf.

3. Pickling

Once the surface has been covered with mold, the leaves are ready for pickling. The leaves are stuffed into a wooden bucket and mixed with the leaf juice from the steaming process. A heavy stone is then placed on top of the leaves, and the pickling process begins. Over the course of several weeks, lactic acid bacteria continue to ferment the tea leaves, resulting in a pickled flavor and aroma that is unique to each batch of tea.

4. Cutting

After fermentation, the leaves are cut into 3-4 cm cubes with a special knife.

5. Drying

These cubes are then sun-dried on a straw mat, resulting in the black color of the tea leaves. Goishicha tea gets its name from the color and positioning of the tea leaves.

January 08, 2023