The Harney & Sons Guide to Tea - Michael Harney [56]
British Legacy Teas share a briskness that comes from being oxidized very quickly. Likely because the British have long preferred a brisk tea, tea makers in the former British colonies roll their leaves into much finer particles. They then spread the particles in thin layers, often blown with heated air, which maximizes their exposure to oxygen. Orthodox British Legacy Teas are allowed to oxidize longer and more slowly, so they have more complex aromas.
In contrast, British Legacy CTC teas are the most astringent of all, as they oxidize virtually instantaneously. CTC stands for “crush, tear, and curl,” the three stages of the “rolling,” or crushing, process: The leaves are not rolled but pulverized, crushed through a fine sieve to tear into tiny shreds that curl into fine pellets. These pellets pass along a conveyor belt under powerful blowers; within the space of one hundred feet and a few hours, the pellets have switched, chameleonlike, from bright green to a flat, dull brown. These teas have almost no thearubigins; their tannic theaflavins make them robustly brisk and mouth-puckering. These teas taste so good with milk because the dairy proteins bind with the tannic compounds to soften them.
While oxidation turns buds gold, it darkens mature tea leaves almost to black. The source of the darker color is chlorophyll, which degrades during oxidation to murky brown pheophytins and pheophorbides. Buds contain very little chlorophyll, and what little they have dissolves during withering. For this reason, oxidation of buds reveals only the golden and coppery colors of degraded polyphenols.
FERMENTATION
Until recently, the process of oxidation was thought to be fermentation. Up until the mid-1900s, tea makers assumed that yeasts and bacteria turned tea black by converting sugars to alcohol the same way wines and breads ferment. In fact, only puerh tea ferments, and the puerh-making process is such a closely guarded secret that it’s hard to know exactly how this happens. But we can speculate: As the teas age, sugars within the leaves are converted to monoterpenoids, which in turn oxidize and degrade over the years into sesquiterpenoids. Sesquiterpenoid compounds have the earthy and camphor flavors that puerhs are known for.
FIRING
The final step in tea production, firing preserves teas by almost completely removing any remaining moisture. “Drying” would be a more accurate term; if the leaves’ moisture is reduced to 3 percent, the tea is stable and no more chemical reactions can take place. It can then travel. In ancient China that meant to the next province; now it means anywhere around the globe.
Depending on how heavily it is done, firing can also profoundly affect a tea’s flavor. Today, teas are commonly dried in ovens or woks. The Chinese originally dried tea over wood fires, which is how the drying process got its name. Over time, wood was replaced with charcoal, a more enduring and even source of heat. Today, the only teas still fired with wood smoke are the Chinese black tea Lapsang Souchong and the oolong Da Hong Pao. By far the majority of teas are dried in electric ovens. Before all the moisture is lost, the heat of the dryers can provoke the same Maillard reaction that sweetens Chinese green teas. The Maillard reaction provokes the formation of dimethylpyrazines, which make for the chocolate and cocoa notes in New Vithanakande Ceylon tea and Keemun Chinese black teas. It also bolsters the honey and malt qualities of Assams. The best teas have the finest roasted aromas because they have the most amino acids.
Firing can also take flavors away: Some of the floral