The black tea you usually drink is “oxidized tea.” This article is all about the most commonly consumed tea: oxidized tea (black tea).

What is oxidized tea (black tea)?

Oxidized tea is a tea whose leaves have been fully oxidized. “Black tea” is oxidized tea.

There are many cultivars and types of tea, but there are basically only two kinds: Chinese and Assam. Most types of oxidized tea are made from Assam tea trees, whose leaves are easier to oxidize.

Features of oxidized tea’s (black tea’s) flavor, aroma, color

Oxidized tea (black tea) is featured by a beautiful red color and aromatic, glamorous, gentle scent and flavor. Of course, oxidized tea (black tea) varies a lot in flavor and aroma by the production area’s climate and natural features. In particular, the world’s three major black teas; namely, Darjeeling tea from India, Uva tea from Sri Lanka, and Keemun tea from China have distinctive flavors and aromas, which are totally different from our usual black tea from a plastic bottle or a tea bag. The wide variety features oxidized tea (black tea) and attracts us.

Features of oxidized tea ingredients

Besides the leaf’s original ingredients, oxidized tea (black tea) contains ingredients produced by the oxidation of tea leaves. Theaflavins and thearubigins are representative of the ingredients that produce an aromatic scent and make a beautiful red color of the tea.

Features of oxidized tea process

As its name suggests, oxidized tea is a tea that has undergone oxidation. Black tea goes through the process called rolling to activate oxidative enzymes that are important to produce the tea’s aroma, flavor, richness, and liquid color. Then it undergoes the processes including oxidation, drying, and sorting (grading) to hit the shelves of stores.

Oxidized tea (Black tea)

Lastly, let us see oxidized tea’s production areas and origin.

Major production areas of oxidized tea

In Japan, the mainstream is green tea. In fact, black tea is produced in over 20 countries and accounts for 70% of the world’s tea production. In particular, the following areas are well-known.

India

India is famous for black tea. Its production volume of black tea is by far the largest in the world and amounts to 1 million tons per year. Darjeeling tea from India is chosen as one of the world’s three major black teas. Its pleasant aroma is praised as “the champagne of black teas.” It is also consumed a lot in Japan. For your information, Assam tea, which is as famous as Darjeeling tea, is also from India.

Sri Lanka

Black tea from Sri Lanka is called “Ceylon tea” and beloved all over the world. Sri Lanka is the producer of Uva tea, one of the world’s three major black teas. Sri Lanka is growing tea mainly around a chain of mountains. Tea in Sri Lanka is graded according to the altitude. The production volume of black tea is the second largest in the world and amounts to 320 thousand tons.

Kenya

Most Japanese people think of Kenya as a coffee producer. However, it actually produces the third largest amount of black tea in the world, or 300 thousand tons, closely behind Sri Lanka. They export it mainly to Europe. Surprisingly, their history of tea is long. They started making tea plantations during the First World War.

China

China produces “Keemun tea,” one of the world’s three major black teas, while we only think about its Chinese tea such as oolong tea. In fact, China is the birthplace of black tea. The annual production volume is 50 thousand tons. Although the number is comparatively less than the other black tea producing countries, the volume is rapidly increasing with the recent focus on black tea production.

Japanese black tea

It is less known but Japanese black tea has been produced since the Meiji Period. The high-quality Japanese black tea won a gold prize at an international food competition. It would suit everybody’s tastes with easy-to-drink, mild flavor and aroma.

Indonesia

Indonesia’s black tea production is currently only the 4^th in the world. However, the country had as much black tea as India until the Second World War burned off their tea plantations. Their tea has similar features to Ceylon tea. Its characteristic mild, easy-to-drink flavor somewhat lacks richness so it is mainly used for blending. The annual volume is 130 thousand tons.

The origin of black tea

The history of tea originated in China. It dates back to a period before Christ. However, the history of black tea is comparatively new; it started after 1720. Black tea has several possible origins, but it is likely that “Wuhan tea,” a semi-oxidized tea, which was collected in Fujian Province, became the mainstream of tea in Western Europe, and developed into today’s common black tea after trials and errors including the increased degree of oxidation. Later on, Assam cultivars suited for black tea were found in India, which promoted tea cultivation in India and other surrounding countries like Sri Lanka. Then, black tea spread all over the world.

<Related Link>

How to Brew Nice Black Tea

Manufacturing Process of Oxidized Tea(Black Tea)

What Kinds of Ingredients/Nutrition are In Black Tea(Oxidized 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.

Did you know that green tea, black tea, oolong tea, and other teas we usually drink, which differ in taste, aroma, and color, are all made from the same tea leaves?

These teas have different tastes and aromas due to the differences in their production methods.

In this article, we will explain why black tea is called fermented tea and how the aroma of black tea is produced, along with the manufacturing process.

Characteristics of manufacturing process of oxidized tea (black tea)

The fermented tea is tea made through complete enzymatic fermentation.

Contrary to unoxidized teas such as sencha and deep steamed sencha, fermented tea is oxidized and fermented using the oxidizing enzymes in the tea leaves.

Initially, it was an "ingenious process (handmade process)" that originated in China about 200 years ago, but nowadays, it is often made by machine.

There are two main production methods: "orthodox" and "unorthodox," A combination of the two has also been produced.

Here we introduce the traditional "orthodox" method.

Fermentation or oxidation?

Fermentation, as used in the tea world, refers to oxidation caused by oxidizing enzymes in tea leaves, as opposed to fermentation caused by microorganisms (bacteria) such as miso or yogurt.

Oxidation is a reaction in which oxygen and enzymes combine to change the original ingredients.

Microorganisms, such as post-fermented teas, ferment some teas, but the tea industry refers to this oxidative fermentation as fermentation.

From plucking fresh leaves to shipping them

Tea leaves are grown in a tea plantation. The tea leaves plucked in the picking season become Aracha (crude tea) after kneading and drying. Then, through “finishing,” the tea becomes a product to be shipped.

How to make Aracha

The plucked fresh leaves undergo the processes of withering, rolling, ball breaking/sieving, oxidation, and drying in this order to become Aracha. Then, after the finishing process, the tea is shipped across the country.

1. Withering

Wilting the fresh leaves to remove the water content evenly is called wilting.

In the past, the leaves were often dried in the shade, but nowadays, "artificial wilting," in which wilting is carried out in a wilting tank with a large amount of warm air, is used.

2. Rolling

The cells of the tea leaves are broken down and shaped by the oxidizing enzymes in the leaves.

When the oxidizing enzymes are exposed to oxygen in the air, they are activated, and catechins, pectin, and chlorophyll undergo oxidative fermentation. These oxidative enzymes are the key elements that create black tea's aroma, taste, richness, and watercolor and lead to the differences between black and green tea.

The tea is fermented for 45 to 90 minutes. Still, to prevent the oxidative fermentation from advancing too quickly, the tea is put through a ball breaker to suppress the fermentation process, cooled, and then repeatedly rubbed again.

3. Ball breaking/sieving

Since the tea leaves clump together during the rubbing process, they are unraveled to allow for average exposure to air, which further promotes oxidative fermentation. The tea leaves are put through a ball unraveling machine during this process every 20 to 30 minutes.

The tea leaves are sieved through a mesh, and those sieved down are called "under the sieve" and transferred to the following process. The larger leaves on the sieve are called the "top of the sieve" and are returned to the twisting process.

4. Oxidation(Fermentation)

In a fermentation chamber with room temperature set at 25-26°C and humidity at 90%, tea leaves are spread evenly to a thickness of 4-5 cm and left to ferment for 2 to 3 hours. During this process, the green leaves turn a bright reddish-bronze color, and a tea-like aroma waft through the air.

However, if the tea leaves ferment too much, the original aroma of the tea will be spoiled, and the watercolor will turn black. Hence, it is necessary to determine when to stop the fermentation process.

5. Drying

Tea leaves at the end of fermentation still have a high water content, and if they are left as they are, fermentation will continue, so they are placed in a dryer and dried with hot air at a temperature of around 100 degrees Celsius. Drying inactivates oxidative enzymes and reduces moisture to less than 5%.

Finishing

The tea after drying is already called “Aracha,” but it cannot be shipped as a product yet. In the finishing phase, it undergoes sorting/shaping and blending in this order to be ready to ship as a product.

6. Sorting (Grading)

Aracha goes through a sifter several times to be sorted by the size and shape. Sorting classifies the tea leaves into grades. This grade is called “leaf grade.”

7. Blending

The final step is blending the leaves. Over 20 types of tea leaves are used, but the purpose is not to mix various kinds. It is to stabilize the quality by choosing teas from the same production area. Blending influences the price of each black tea, and what matters is how to suit consumer tastes by blending.