Tea Processing
Production of tea varies widely according to the desired end product. Basically, all tea leaves must at least be picked and dried. With all tea, drying to a level of two to three percent moisture makes the tea shelf-stable. Good tea requires greater care.
Over centuries more styles of processing have developed than can be easily summarized. The steps described here introduce you to some basic techniques, which may be repeated and modified throughout the process to better control the outcome. After the leaves are picked, they may be manicured to separate the youngest leaves, essentially grading the tea while it is still fresh. Sorting, cleaning and grading may take part at the end of production as well.
White Tea
White tea is known as the least processed of teas. The harvested leaves are spread in an open area to allow air circulation for the withering process. During withering, the leaves experience cell death, becoming pliable and aromatic. Brief withering sweetens and mellows the raw tea. If this were allowed to continue, the leaves might begin oxidation in earnest, turning dark or even rotting.
Green Tea
Following harvest, Japanese greens are steamed to prevent withering, insuring bright green color and an assertive raw flavor. The resulting bitterness is sometimes balanced by shading the plants for weeks before harvest. Lack of sunlight changes the chemical composition of the leaves, making them very sweet. The best leaves are either rolled to needle shapes, or pressed into flakes for grinding. Heavy steaming can make the finished tea leaves very broken up. Partially processed teas may be stored at cool temperatures for later processing.
Chinese greens rarely end up so raw. Usually some withering is allowed. Oxidation is typically ceased by forced hot air, rubbing the leaves against a hot wok, or firing in an oven. The leaves reconstitute slightly as moisture migrates from the center outward to the surface. The tea may then be rolled, twisted, pressed or tied by hand into traditional decorative shapes, as are oolongs and blacks. Jasmine tea is made by taking the green tea produced in the spring and exposing it to blooming jasmine buds in the summer.
Oolong Teas
Oolong teas use the larger, lower leaves on the branches. This makes more manipulation possible without destroying the leaves. After withering and initial heating, rolling and heating may be alternated for days, allowing great control. The end product may be as green as green tea, or as dark as black tea. It is the leaf type and process that define oolongs, rather than the level of oxidation as is the case with blacks and greens. The final firing is sometimes accentuated to impart a toasty quality.
Black Teas
Black tea follows the same production pattern, but differs in having more time to oxidize and turn dark before final drying. Black tea is essentially oxidized tea. The leaves may even be crushed to expose their juices to air, speeding the process. Sometimes these wet leaves clump together during rolling and another step called "roll-breaking" is added to break them up.