From Leaf to Tin
Every tea in the world, white, green, yellow, oolong, black and the dark fermented bricks of Yunnan, comes from the leaves of a single species, Camellia sinensis. There is no black tea plant and no green tea plant. The differences that fill a tea shop are made in the forty-eight hours after the leaf is picked, by a handful of steps that a tea maker applies in different orders and to different degrees: letting the leaf wilt, bruising it, letting it brown, and heating it to stop the browning. Understand those four steps and the whole wall of tins makes sense. Our loose-leaf guide covers how to brew the result; our tea history covers how it got here. This is what happens in the factory.
The leaf
Quality begins with the pluck. The finest teas take only the bud and the top two leaves of each shoot, by hand, in the early morning, because those are the youngest, most tender and most concentrated in the compounds that matter. Lower leaves are tougher and flatter in flavor. The plant is a relative of the garden camellia, an evergreen shrub kept waist-high by pruning that would grow into a tree if left alone, and it grows best in mist and altitude, which is why the great tea gardens are on hillsides from Darjeeling to Uji to the Wuyi mountains. Inside the fresh leaf are three things that decide everything: polyphenols, the astringent compounds that will brown when exposed to air; enzymes that drive that browning; and the aromatic oils and amino acids that give tea its flavor and body.
Step one: withering
Fresh leaves are spread on racks, trays or long troughs and left for several hours to a day in gentle air. They lose a third or more of their water, go limp and pliable, and begin to change chemically: proteins break into amino acids, grassy notes soften, and the cell walls weaken so the next step can work. Almost every tea is withered to some degree. White tea is withered longest and most gently, sometimes for days, and then simply dried, so that its whole character is the wither: pale, soft, faintly sweet, hay and honey.
Step two: bruising and rolling
To make anything other than white tea, the leaf's cells must be broken so that the enzymes inside meet the polyphenols and the air. Traditionally this is done by rolling the withered leaves by hand on a bamboo tray or against a table, twisting them into the curled and spiral shapes that unfurl in a cup; machines now do most of it, pressing and rotating the leaf under weight. For oolong, the bruising is deliberately partial, often by tossing and shaking the leaves in baskets so that only the edges are damaged. For black tea, the rolling is thorough, and the leaf is broken open completely.
Step three: oxidation
This is the step people call fermentation, and it is not one; nothing ferments. It is the same browning that happens to a cut apple. The enzymes released by bruising act on the polyphenols in the presence of oxygen and turn them into new, larger compounds that are darker in color and rounder, less astringent, more complex in flavor. The leaf changes from green through copper to brown, and the aroma changes from grass to fruit to malt and honey. The tea maker controls it with time, temperature and humidity in a warm, damp room. Black tea is allowed to oxidize fully, for several hours, until the leaf is uniformly dark. Oolong is stopped partway, anywhere from about ten percent for the greenest, most floral Taiwanese styles to seventy percent or more for the dark, roasted Wuyi rock teas, and that range is why oolong is the widest category in tea. Green and white tea are not oxidized at all, or barely.
Step four: firing
Heat stops the enzymes. When the tea maker decides the oxidation has gone far enough, the leaf goes into heat, and the moment and method of that heat is the last great decision. For green tea, the heat comes almost immediately after picking, before any oxidation can start: in China, the fresh leaves are tossed in a hot dry wok or pan, which gives Chinese greens their toasted, nutty, chestnut notes; in Japan, they are steamed for under a minute, which locks in the bright, grassy, marine flavors of a sencha or a gyokuro. For oolong and black tea, the firing comes at the end, drying the oxidized leaf in ovens or pans to a few percent moisture so it will keep. Many oolongs are then roasted a second time, gently, over charcoal, for the deep caramel notes of a traditional Tieguanyin or Da Hong Pao. A tea that is fired well tastes clean; one fired badly tastes burnt or, worse, flat and wet.
The exceptions
Yellow tea is green tea given a brief, warm, covered rest after firing that mellows its grassiness. Dark tea, including the pu-erh of Yunnan, is the one case where the word fermentation is correct: the finished leaf is piled damp or pressed into cakes and allowed to age under microbial action for months or decades, developing earthy, woody depth and a following as devoted as any wine's. Scented and flavored teas, like the jasmine greens of Fujian or the fruit-and-flower blends in our Mariage Frères guides, begin with a finished tea and add the scent afterward, by layering with fresh flowers or spraying with essences; the base tea's processing still decides most of what is in the cup.
What each step puts in the cup
The wither gives softness and sweetness. The roll gives shape and, in the cup, how quickly the leaf releases its flavor. Oxidation gives color, body and the shift from grass toward fruit and malt; it also lowers astringency, which is why a black tea can take milk and a green tea cannot. The firing gives the toasted or steamed character and decides whether the tea will keep for a year or fade in a month. When a tea guide says a Darjeeling first flush is light and floral while a second flush is fuller and muscatel, it is describing two different withers and oxidations of the same bushes a few weeks apart. When it says a Japanese green tastes of the sea and a Chinese green of chestnuts, it is describing steam against a wok.
Reading it on the tin
The category on a label, white, green, oolong, black, is a statement about oxidation. The origin is a statement about the leaf and the climate. Words like "pan-fired," "steamed," "charcoal-roasted" or "first flush" are statements about the steps above, and they are the words worth learning, because they predict the cup. The teas on our tea shelf are at 263 Josephine Street in Cherry Creek, Denver, and ship nationwide from theambrosianpantry.com. Brew a green and a black from the same region side by side, per our loose-leaf guide, and taste the two days of work that separate them.
