The Harney & Sons Guide to Tea - Michael Harney [54]
On the opposite end of the spectrum, high-mountain oolongs, First Flush Darjeelings, and some high-grown Ceylons wither for several hours more—not just to provoke the aromas, but also to dry out the leaves and concentrate the compounds. Over so much time, fatty acids continue to degrade into yet more aromatic compounds like the geranium-scented geraniol and jasmine-scented methyl jasmonate. The aromatic compound methyl salicylate gives Uva Highlands Ceylon black tea its remarkable minty aroma. In addition to fatty acid degradation, in black teas and darker oolongs, which continue to wither as they oxidize, the pigment carotene starts to degrade into the aromatic compounds ionones, damascones, and damascenones, forming delicious fruity aromas reminiscent of apricots, peaches, and honey.
The scent of withering tea is incomparable—fresh and floral, far more vibrant than the final scents of brewed tea. Like a tea man’s perfume counter, tea factories at the peak of harvest throb with aromas of lemon, jasmine, and apricot. I love to walk through them, smelling handfuls of the withering leaves.
FIXING
Makers of green teas bring all this aromatic activity to a halt when they “fix” the leaves, cooking them to keep them green. In the fruit and vegetable world, this reaction is called “enzymatic browning” and affects a host of ingredients including bananas, avocados, potatoes, and apples. If you slice open a potato, within a few minutes the exposed flesh will begin to darken. If you cook the potato, it will remain white. Tea makers similarly rapidly increase the leaves’ internal temperature to 160 degrees Fahrenheit, deactivating the enzyme polyphenol oxidase, or PPO, that would otherwise turn them brown. (Another way to deactivate PPO is to deprive the enzyme of water, which it also needs to perform its duties. Uva ighlands Ceylon tea and First Flush Darjeelings desiccate so severely after harvest that they undergo what’s called a “hard wither,” drying out in heated troughs to such an extent that they become partially fixed, like green teas.)
The fixing method impacts the tea’s final taste. Imagine the difference between a steamed potato wedge and a browned, roasted one and you have a sense of the difference. Japanese green-tea makers steam their leaves in tunnels, giving the teas the more assertive, vegetal flavors of steamed spinach. Since World War II, some Japanese tea makers have begun steaming the leaves twice as long, for up to a minute instead of the traditional thirty seconds. The increase may seem slight, but it results in an even more assertive tea.
Certain Chinese green teas like Bi Lo Chun and Lung Ching have the lighter, slightly sweeter flavors of toasted nuts and steamed bok choy in part because Chinese tea makers sear the leaves over woks. The much hotter pans and ovens trigger what chemists call “the Maillard reaction.” Named for Louis-Camille Maillard, the French chemist who first studied it at the turn of the last century, the reaction creates pyrroles, pyrazines, and other compounds tasting of baked peaches, roasted nuts, and similar baked or roasted flavors. A form of nonenzymatic browning, the Maillard reaction also darkens the teas somewhat.
Woks and ovens also give Chinese green teas a slightly wider range of aromas. Leaves reach 160 degrees Fahrenheit almost instantaneously when they are steamed, but they can take several minutes to heat up in a wok or a hot oven. Until they are fixed, the leaves continue to wither, producing yet more aromatic compounds. A comparison of the aromas in a Japanese Sencha and a Chinese wok-fired green tea shows that the Sencha has more lemony linalools, while the wok-fired tea has more carroty beta ionones and neriols, floral aromas more common to oolongs, which wither for a much longer period. Although