The Harney & Sons Guide to Tea - Michael Harney [52]
HARVEST
Flavor begins in the fields. Scientists have identified over six hundred flavors and aromas in tea, many with obscure and wonderful names like “linalool” and “hexanol.” The miracle is that tea makers create these hundreds of flavors from only six classes of chemical compounds that all reside within the tea plant: color pigments, sugars, amino acids, fatty acids, caffeine, and polyphenols. These compounds exist in nature to nourish and protect the plant against attack. The aromas and flavors we find so enticing in tea actually deter aphids, leafhoppers, and other insects from eating the leaves. In essence, tea makers pose as insects, damaging the leaves to provoke them to defend themselves—and, in the process, rendering them delicious.
The first secret to flavorful tea is to gather the leaves at their peak, when they contain these compounds in the most mouthwatering proportions. With the exception of tropical teas from Assam and Ceylon, the finest teas peak in the spring.
Like all plants, tea bushes grow through photosynthesis. The color pigments chlorophyll and carotene absorb sunlight so that the plant can convert carbon dioxide and water into glucose and other sugars. When the sun fades in the winter, the bushes go dormant, storing nutrients in their roots. As the winter dormancy ends and the temperature warms, the plants draw on these nutrients to create more leaves. The plant forges amino acids to build proteins. And it produces caffeine and polyphenols to repel bugs and protect the plant from attack. The two chemicals appear to disorient herbivores, dissuading them from eating the leaves.
Caffeine and polyphenols are likely of most interest to the tea drinker from a practical standpoint. After all, many of us drink the beverage every morning for its ability to wake us up. And a growing percentage drink it to stay healthy, although the “health via antioxidants” claim remains inconclusive. It is safe to say that the polyphenols in tea act as antioxidants, but scientists are still establishing what antioxidants do. They appear to reduce the effects of free radicals, molecules that may interfere with the healthy expression of DNA, provoking the mutations that may lead to tumors. Thus tea may help stave off cancer as well as heart disease. We just don’t know for sure. Luckily, no scientific studies exist to prove that tea is not healthy.
I would also love to be able to give definitive numbers about the levels of caffeine in these different teas, but the amount of caffeine varies too much—both from one plant to another and within the different teas—to offer any specifics. White teas likely have more caffeine than green teas or black teas because buds have more caffeine than mature leaves. And tea generally has about a third the caffeine of coffee. If you are trying to avoid caffeine, the best advice I can give is to drink herbal tea. Tea makers can remove caffeine from tea by rinsing the leaves in either ethyl acetate or supercritical carbon dioxide—liquid CO2. Both are safe, but both leach out the more nuanced flavors along with the stimulant.
For tea connoisseurs, caffeine and polyphenols each affect a tea’s flavor along with sugars, amino acids, and fatty acids. Sugars obviously make the tea sweet. Fatty acids provide tea with many of its aromas. Amino acids influence body, giving teas their relative brothiness, or umami. One amino acid in particular, called “L-theanine” (“theanine” for short), seems to create the most mouth-filling qualities. Japanese tea makers frequently speak of the favorable theanine levels in their best teas. Theanine has also been increasingly studied for its ability to soothe the brain and enhance concentration, making tea a gentler stimulant than coffee. Caffeine, an alkaloid, gives tea a mildly bitter bite. Polyphenols furnish tea with its tannic qualities, its relative astringency or briskness. Two have a particularly strong effect: EGCG, or epigallocatechin-3-gallate, a