HERBS for HEALTH
Green tea has taken the Western world by storm. Once a favorite of Asian peoples alone, this ancient beverage now charms Westerners alike. As a health brew, green tea may inhibit several types of cancers; delay age-related cancer onset; boost immune function; reduce LDL cholesterol, blood sugar and risk of stroke; curb severity of rheumatoid arthritis; alleviate pain; and combat tooth decay.
The key is catechins, a specialized group of polyphenols that gives green tea its astringent flavor and confers many of its health benefits by serving as antioxidants, antiseptics and detoxifiers. Green tea, the best dietary source of catechins, contains at least eight types, mainly epigallocatechin gallate and epigallocatechin. Compared to its fermented sisters, oolong and black tea, green tea retains more catechins — as much as 30 to 42 percent of dried leaf weight versus only 9 percent in black tea.
Almost 90 percent of green teas are from China, but types from Japan and elsewhere also are popular. While all green teas are of the species Camellia sinensis, differences in origin and processing create many varieties.
Chinese green teas include renowned names like Lung Ching, Pi Lo Chun, Mao Feng, Yin Zhen, Yun Wu, Mao Jian and Gua Pian. These regional teas are famous culturally for their individual leaf characteristics, color, aroma and flavor. The best known is a tea from China’s Zhejiang province, Lung Ching, whose flat leaf buds yield a pale jade tea with a floral aroma and fruity taste. Chinese teas range considerably in quality, but the most prized are those whose young leaves or leaf buds are plucked very early in spring and hand rolled to final shape. Premium teas can cost more than $10 per ounce, lesser ones about $5.
More common Chinese green teas include Young Hyson, gunpowder and Chun Mee. Gunpowder and Young Hyson varieties consist of leaves rolled into pellets, or twisted in a long thin style, respectively. These everyday teas typically cost less than $2 per ounce and taste harsher and less complex than the more expensive varieties. This is especially true of gunpowder tea.
Flavored teas are a special treat. These teas bear the fragrance and flavor of jasmine, citrus, mint, rosebuds, vanilla and other botanicals. Chinese jasmine tea remains a favorite — the tea leaves are dried with jasmine flowers, which, when removed, leave behind a subtle fragrance and taste.
Japanese green teas are of two basic types: Sencha and Gyokuro. Sencha, composing 75 percent of Japanese production, is grown in the sun, while Gyokuro is shaded a few weeks before harvest. Premium qualities use only the new spring leaves. Several teas are based on Sencha, including an early-season tea called Shincha, a late-summer tea known as Bancha and a blend of Sencha and toasted brown rice called Genmaicha. Bancha is a low-priced yellow tea with a brisk, harsh flavor. Genmaicha is also inexpensive, and its crispy, milder flavor goes well with meals.
Gyokuro makes a sweeter, darker-green tea than the grassy-flavored Sencha and costs at least $5 per ounce (Senchas start around $2). Gyokuro also is the source for Matcha, the powdered tea used in the traditional Japanese tea ceremony. Matcha is ground from the soft inner Gyokuro leaf, with stems and leaf veins removed. It should not be confused with ordinary powdered green tea, which is made from Sencha and added to shakes, ice cream, breads and other foods.
Buds of either Sencha or Gyokuro can be used to make bud tea or Mecha, a hard-to-find yellow, aromatic infusion with a sharp, bitter aftertaste. The roasted stems and leaf stalks produce stalk tea, or Kukicha, a reasonably priced tea with a nutty-woody aroma and mild, slightly astringent flavor.
A satisfying array of choices — but are they all equal in catechin content?
For tea connoisseurs, balance between astringency and sweetness is paramount, even at the expense of medicinal quality. Some varieties are being bred for lower content of the bitter polyphenols to enhance beverage appeal, but this may diminish the tea’s health benefits. For optimal health benefit, catechins should be preserved throughout tea production, processing and brewing.
A tea’s harvest time is a strong indicator of its catechin levels. Teas harvested in early spring are the richest in catechins. As the season progresses, catechins and sweetness-conferring amino acids decline, more so in unshaded teas such as Senchas than in Gyokuro teas. Late-harvested teas, such as Bancha, are very astringent because they lose their amino acids more rapidly than catechins. Stalk teas are the lowest in polyphenols and other nutrients.
After harvest, producers sometimes allow Chinese green teas to wither in sunlight for dehydration and softening, prior to heating them to sterilize and inhibit fermentation. Then the tea is rolled and dried. Japanese teas are not withered but are steamed at about 212 degrees right after harvest to prevent fermentation, then rolled and dried. Hot-air withering may reduce polyphenols and other constituents because digestive enzymes are still active. Steaming better protects polyphenols, vitamins and amino acids, and helps retain a greener color.
Rolled tea leaves release their nutrients more readily during infusion than unrolled types because rolling breaks up the structure of the tissues. Teas that come as pellets, rolls or twists, and powdered forms may thus be good choices. Stalk tea must be simmered for several minutes in boiling water for proper extraction.
To brew bud, leaf or powdered teas, connoisseurs traditionally shun boiling water because the resulting brews are considered too astringent. The recommended water temperature is between 165 and 185 degrees though gyokuro teas typically are brewed at about 140 degrees. Amino acids dissolve in water at 140 degrees, but catechins dissolve more readily at 176 degrees or higher, meaning much lower concentrations in cool-infused teas. Infusing longer than the usual two to three minutes has only a minor effect, so if you want the most catechins, use hotter water. When making iced tea, infuse the hot water for extraction, then chill the brew over ice.
Caffeine levels vary according to the part of the tea plant harvested. Teas from the buds and uppermost leaves have about four times the caffeine as in the lower stem, with a decreasing gradient in between. Caffeine in green tea, though considered low at 11 to 20 mg per cup versus 120 mg per cup for coffee, still may be problematic for some people. And powdered green tea, such as matcha, while permitting better absorption of catechins by the body, can concentrate caffeine. If a decaffeinated tea is desired, consider those decaffeinated by the spring water or carbon dioxide methods, rather than ethyl acetate and methylene chloride, which can damage antioxidants. In Japan, decaffeinated green tea is almost unheard of except for a tea known as houjicha, which is bancha or kukicha pan-fried or oven-roasted for an agreeable, not-too-bitter taste. But houjicha, while low in caffeine, is unfortunately lower in catechins, amino acids and vitamins, too.
For those worried about pesticides, organic green teas are available. Chinese teas especially have been a concern because of pesticide use in some regions. China is now working to produce more teas that satisfy organic guidelines of nations such as the United States and the European Union. Organic teas from Japan and elsewhere also are available. Look for certification by a reputable organization such as the Japan Organic & Natural Foods Association or another recognized body.
Gina Mohammed, Ph.D., is a plant physiologist in Sault Ste. Marie, Canada. She is author of Catnip and Kerosene Grass — What Plants Teach Us About Life (Candlenut Books, 2002).
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