Manufacturing Process of Fermented Tea

“Pu’ er tea” and “Goishicha” are seen more in our daily life these days. Do you know what makes their distinctive flavors? In fact, microbes play a role to yield those flavors and aromas. The term “fermented tea” that includes “Pu’ er tea” and “Goishicha” is from the method that utilizes microbes. Let us take a closer look at why it started being called “fermented tea.”

Features of fermented tea process

“Fermented tea” is a tea produced by fermenting the leaves with microbes.

In the world of tea, “fermentation” generally refers to oxidative fermentation, caused by enzymes. In contrast, the “fermentation” of fermented tea is caused by microbes such as mold and lactic acid bacteria.

Difference by type of microbes to be used

Two major types of microbes are used for fermented tea. One is mold (e.g. kōji-mold), which likes oxygen, and the other is bacteria (e.g. lactic acid bacteria), which dislikes oxygen. “Pu’ er tea” uses only mold, while “Awabancha” uses only lactic acid bacteria. “Goishicha” uses both of them through two-stage fermentation.

Fermented tea process

The manufacturing process of “fermented tea” varies by type of microbes used. The above “Pu’ er tea,” “Awabancha,” and “Goishicha” also have different processes each other. Let us see what differs with these three examples.

Pu’ er tea

“Pu’ er tea” undergoes fermentation for months or longer with the leaves pickled in kōji mold. In some cases, ripening takes more than ten years. Its flavor and health benefits change according to the ripening degree.

Oxidase deactivation by steaming

The plucked leaves are steamed to deactivate oxidative enzymes in the leaves.

1. Rolling

The leaves are kneaded when they are still hot to uniform the leaf moisture so that the leaf ingredients get easy to come out.

2. Wo doi (Molding)

Add mold to the leaves to ferment under a specific controlled temperature and humidity. This process plays an important role because the tea’s quality, flavor, and aroma depend on its accuracy.

3. Drying

The hardened leaves are loosened by drying to finally become “Pu’ er tea”

Awabancha

“Awabancha” is produced through fermentation utilizing indigenous bacteria that originally live on or in a place like wooden buckets. It is an individual local tea produced in Tokushima Prefecture through many generations.

1. Deactivation by boiling

The plucked tea leaves are boiled to deactivate the leaf enzymes so that oxidative fermentation does not take place. This process is also effective to suppress the propagation of unwanted bacteria.

2. Rolling

Kneading the leaves can evenly spread the leaf moisture so that the leaf ingredients get easy to come out.

3. Pickling

The rolled leaves are stuffed in a big bucket with the boiled soup of the leaves added. Air is removed by poking the leaves from the top. The bucket is covered with the wooden lid and a heavy stone on it. Lactic acid bacteria start fermentation then. Pickling takes 2–5 weeks.

4. Drying after bucket opening

Once fermentation has finished, the leaves are taken out of the bucket and sun-dried. Then through sorting, thick stems and other unwanted parts are removed. Then “Awabancha” is ready.

Goishicha

“Goishicha” undergoes two-stage fermentation using both mold and lactic acid bacteria. It has been produced in Kōchi Prefecture since the Edo Period. The same method has been inherited since then. Indigenous bacteria are also inevitable for this tea. Bacteria that live in a storehouse or in a straw mat have been used for many generations.

1. Deactivation by steaming

Tea leaf picking for Goishicha is not leaf plucking but twig clipping. The leaves picked with twigs are steamed to deactivate oxidative enzymes in the leaves.

2. Molding

The steamed leaves are spread, piled, and left for about a week on a straw mat in the molding room. Fermentation starts then and lactic acid bacteria grow on the tea leaf.

3. Pickling

Once the surface has been covered with mold, the leaves are stuffed into a wooden bucket. After adding the leaf juice from the steaming process, a heavy stone is put on it. Fermentation by lactic acid bacteria goes on as the leaves are pickled for several weeks.

4. Cutting

Once fermentation has been done, the leaf bundle is taken out of the bucket and cut into 3–4-cm cubes with a special knife.

5. Drying

The tea cubes are arranged on a straw mat. After sun-drying, they become “Goishicha.”

The leaves turn black as they get dried. It is said that the term “Goishicha” is derived from the color and positioning of the leaves.