People have been drinking tea for thousands of years. Enjoyed worldwide for its flavor, and both stimulating and soothing properties, tea is the most popular beverage aside from water. The tea bush, Cameilla sinensis, is grown throughout Asia, from assam and darjeeling in India, to Sri Lankan ceylon, to the myriad teas of China. From the moment the fresh leaves are plucked, great care and effort is put into the development of processed tea. Although today the methods of tea manufacturing are aided by machinery, the essential process has remained the same.
Fresh Tea Leaves
As soon as tea leaves are harvested they began to lose their moisture content, a process known as withering. Leaves that are meant to be made into black tea are allowed to wither until the desired amount of water evaporates. This is either done naturally, or heated air is used. The leaves are spread by hand, usually onto a table, or a perforated metal tray.
Next they are treated, usually with a machine. The leaves are twisted, rolled, and crushed. This breaks down the leaf cells and exposes them to air. This is the beginning of the oxidation process, known as tea fermentation. The broken down leaves are then pushed through a sieve to continue the fermentation process. Those leaves that weren't broken down enough initially go through the rolling process again. Once the tea is ready, it is brought to the oxidation room, which is carefully regulated for humidity, temperature, and air circulation.
Oxidized Tea
Tea fermentation is not a true fermentation because no microbes are involved. It is a complex and delicate chain of chemical reactions, the primary one being polyphenol oxidation. According to the Encyclopedia Britannica, polyphenol oxidation is the enzyme polyphenol oxidase, being activated by oxygen exposure. Tea polyphenols react with other compounds to create theaflavins; theaflavins go through further chemical reactions, creating thearubigins. It is these components of tea that are responsible for the specific, desired flavor and color characteristics of black tea.
Black tea is allowed to oxidize until the leaves reach their brownish-red hue. This process usually takes from two to four hours. Heat ends the tea fermentation process. Traditionally, the oxidized tea leaves would be heated in large pans set over a fire, but today tea manufacturers simulate this process with blowing heated air onto the leaves with machinery. The tea is reduced to a final moisture content of 3%. This final step contributes to the rich, sweet taste of black tea, by caramelizing some of the sugars. The leaves are now ready to be packaged and shipped to their destinations around the world.
Differences Between Black, Oolong, and Green Tea Processing
The differences between the various types of true teas lies in the level of fermentation, or the amount the leaves are allowed to oxidize. While black tea is fully-fermented, oolong tea is partially-fermented. The tea leaves are still allowed to start polyphenol oxidation, but the process is stopped once the leaves reach a water content level of 20-50%. Oolong teas are characterized by a pale brown color, and a more fragrant, softer flavor.
Green tea is unfermented tea. Instead of being allowed to wither, going through rolling, and oxidation tea processing, the tea leaves are immediately heated, either by pan-frying, or by hot steam. This method preserves more of the health properties, and produces a delicate, fresh tasting tea.
There are dozens of varieties of true teas, all depending on the subtle differences in tea processing.
 |
