The most widely consumed ancient beverage is the Tea. Camelia sinensis is the botanical name of the tea plant. Tea processing involves various steps like plucking, withering, crushing, drying, rolling and shaping of tea leaves through which the leaves are made ready for brewing. In ancient China tea consumption was originated and reached the European continent in the 16th century. In India, tea was cultivated in Assam in the 19th century. Chinese variety (C. s. Sinensis), and Assamese variety (C. s. Assamica) are the two basic varieties of tea from ancient time. The practice of steaming fresh tea leaves and drying them for further storage and consuming it by decocting with other herbs was followed in China. Want to know more about tea growth and harvesting? Read Pritish Halder article below.
Tea Growth and Harvesting
Growing conditions have a large impact on the flavor of tea. The terroir, or growing environment, is an important contributor to tea flavor. Changes in climate, soil, and surrounding vegetation subtly change the leaf and affect the final tea.
Tea leaves are picked from Camellia sinensis bushes up to four times a year. Tea made from flushes, which include the terminal bud and two young leaves, are the highest quality teas with the finest flavors and aromas. This type of harvesting is called fine plucking. Fine plucking is done by hand in many countries. Tea harvesting employs millions of people around the world.
Coarse plucking, which uses tea flushes and mature leaves, can be achieved using simple clippers. Machine harvesters can also be used. Due to the presence of additional cellulose and woody structures, the quality of the flavor and aroma in machine-harvested tea may be lessened.
As mentioned previously, all tea is produced from the same plant, and it is the processing that determines the type of tea produced. Tea type is largely determined by the level of oxidation, which increases from white to green to oolong to black teas. Each of the processing steps employed in tea production has a distinct effect on the final product quality and characteristics.
Withering of Tea Leaves
Tea leaves begin to wilt soon after picking with gradual onset of enzymatic oxidation. Withering is used to remove excess water from the leaves, as well as to allow a slight amount of oxidation. Leaves are typically withered by spreading them out on fabric or bamboo mats in either the sun or a breezy room. Humidity and temperature are monitored, and the leaves are rotated. Withering can result in up to 50% moisture loss. The process is important to promote breakdown of leaf proteins into free amino acids and increase availability of caffeine, both of which affect the flavor of tea. Withering is also important in making the waxy tea leaves flexible so they won’t crumble during the remainder of processing. All tea types are withered, although using different conditions.
Mechanical Processing/Disruption of Oolong and Black Tea Leaves
After the leaves are withered, a variety of methods can be used to mechanically damage/disrupt the tea leaves. The purpose of this step is to break down the cell walls in the leaves to facilitate oxidation. This step is employed for processing oolong and black teas, which require greater levels of oxidation. Leaves must be thoroughly and evenly bruised to produce consistent tea. Some dark teas undergo multiple rounds of bruising and/or cutting, tearing, and curling (CTC). In the orthodox method, gentle rolling is performed either manually or by machine to release moisture, coating the surface of the leaves with juices and preserving the whole, unbroken leaf structure. Alternatively, the CTC method is used. This is performed by a machine that chops the leaves into small pieces.
Oxidization Process for Oolong and Black Tea Leaves
Oxidation is an important chemical reaction and process step for the final flavor of the tea. As well as its appearance and color. The leaves are typically spread out in a cool, damp atmosphere to facilitate the oxidation process. This is often accompanied by agitation. In this process, the chlorophyll in the leaves is enzymatically broken down and tannins are released and oxidized. Black teas are highly oxidized (100%), which produces the darkest-colored and strongest-flavored teas. Oolong teas vary in oxidation from about 5% to 70% oxidation. Green and white teas are not oxidized.
Fixation or Kill Greening of Tea Leaves
Fixation is performed to stop oxidation at a desired level. This step is sometimes called kill green because it preserves the green color of the tea. This process is accomplished by mildly heating the tea leaves, thus denaturing the enzymes responsible for oxidation. The mild heat also helps remove undesirable odors from the leaves while preserving their flavor. There are two traditional processes for fixation. The first is pan roasting in a wok and is traditionally done in China. The second is steaming, which is typically performed in Japan. These two processes produce different flavored teas. More recently, baking or panning has been performed in large rolling drums. All teas other than black teas require fixation.
Damp leaves can be rolled by hand or with rolling machines to cause the tea leaves to wrap around themselves. This rolling action also releases some of the sap and essential oils in the tea leaves and enhances the final flavor of the tea. A variety of shapes can be formed, including spirals, pellets, balls, and cones. In many types of oolong teas, the leaves are shaped in large cloth bags that are kneaded by hand or machine. Alternately, the leaves may be pressed into bricks using heavy stones or presses.
Finally, all tea types must be dried to remove any residual moisture and create a shelf-stable tea. This step is typically accomplished through baking and can dramatically change the tea flavor. Alternately, panning, sun drying, or hot air drying can be used for dehydration. Charcoal roasting is sometimes used to impart a distinctly rich quality to the flavor during this step. In contrast, gentle drying can be used to avoid any flavor changes. White tea, for example, is typically dried very gently for long periods of time to replicate traditional sun drying processes.
Sorting, Bagging, and Packaging -After tea is dried, it is sorted, bagged in some cases, and packaged.
Recent Innovations in Tea Processing
Several innovation fronts are being explored for teas. The first is farming tea in the United States, which has seen expansion in recent years. In addition, fermented, ready-to-drink kombucha teas are becoming increasingly popular among health-conscious consumers. Tea-infused alcohol is also being introduced in Japan. Recent research has focused on novel fermentation and drying methods for tea. Finally, research on tea processing and how that impacts the nutritional value of teas is ongoing. The next time you sip this remarkable beverage, try to be mindful of all that went into making it.