WHAT IS GREEN TEA?Green tea is leaves from the tea plant (Camellia sinensis) that have been heated up to high temperatures shortly after picking, which will leave them unoxidized and green in color, and the taste will stay very similar to freshly picked tea leaves. The aforementioned heating, also called "fixing", "de-enzyming" or "kill-green", is done to deactivate the oxidative enzymes within the leaves. If the leaves were left to oxidize, they'd end up as white tea, black tea or oolong tea, depending on other processing steps.
Did you know? The oxidation in tea leaves is a similar process to the one in fruits and many vegetables. It's called "enzymatic browning" or "food browning", and it's caused by enzymes (e.g. polyphenol oxidase) that oxidize the phenolic content in the plant. When a plant cell is damaged, e.g. due to drying or crushing, its enzymes and phenols mix together which starts the oxidation. When tea oxidizes, the greatest physiological change comes from catechins within the fresh leaf transforming into theaflavins and thearubigins. Oxidation significantly alters the tea's flavor.
In China, the fixing of the tea leaves is usually done by firing them on a pan or in a basket, or sometimes putting them in an oven – not until dry, though. In Japan, tea is de-enzymed by steaming them, which also softens and breaks up the structure of the leaves. In South Korea, both pan-firing and steaming are common, although distinctly Korean-style tea calls for pan-firing.
After fixing, green tea gets shaped. The leaves are usually rolled into curls or needles, and in some cases they're flattened. Shaping helps break down the cell walls, which in turn helps the tea release good flavors when brewed. It also makes the dry leaves sturdier and more compact. The leaves might still get a light roast after drying, as is common especially in Japan.
Green tea has been drunk in China at least since the Tang dynasty times (619–907) when it was customary to compress tea into cakes that then were broken up and ground up into a rough powder that was then boiled in a cauldron. In Song dynasty China (960–1279), green tea was ground up into an even finer powder and then mixed into water in a bowl using a bamboo whisk. In the 1100s, tea was permanently brought to Japan in such a form, and it's still produced there as matcha. Modern-style loose-leaf green tea has been made at the latest since the early Ming dynasty, as the Hongwu Emperor decreed in 1391 that tea be produced in loose-leaf form and the powdered form should be abandoned. In the western countries, green tea and oolong tea were virtually the only tea categories of the 1600s and 1700s, as black tea wasn't available until the 1800s.
GREEN TEA'S PROPERTIES AND BENEFITSOf all the main categories, green tea's flavor and aroma are the lightest and freshest, and it has characteristic grassy, vegetal or even marine notes. Some bitterness in the taste and a somewhat astringent mouthfeel are a normal element in green tea, and they can be managed with a lower brewing temperature. Chinese teas tend to have a light, smooth and vegetal character; Japanese teas usually have explicit grassy or seaweed notes, a richness of taste, and a thick and dry mouthfeel; Korean teas have a clearly defined taste, usually with a nutty aroma. Green tea also has an especially vibrant feeling of freshness when you get to try a tea within a few months of its picking and processing. Not that it would go bad after that, but fresh green tea is the big tea event of each spring and early summer, at least in tea shops.
My subjective observation is that green tea rejuvenates a tired mind more efficiently than other categories, and it's especially refreshing and even cooling during the warm seasons. Green tea is generally best as is, without anything added and without snacks on the side, because the tea's light taste is easily covered, especially by fat and sugar. On the other hand, it was common at least in 1700s Europe to make a strong brew of a bold-tasting green tea (like Gunpowder or Chun Mee) and then add brown sugar and cream or milk to it. Worth a try, maybe?
Did you know? Green tea has gotten special attention in the media on account of its antioxidative catechins and other health benefits. It's rarely noted though that the theaflavins and thearubigins (oxidized from catechins) that are present in other tea categores are also antioxidative, and that studies have shown that all tea categories have very similar effects in general, which isn't surprising as they're all from the same plant species. If you hear hype about green tea's health effects, it probably applies to all the tea categories!
GREEN TEA AND CAFFEINEAs a whole category, green tea is not that suitable to drink just before going to sleep because it contains the same amount of caffeine as other tea categories on average (ca. 20–30 mg caffeine in one gram of leaf), and many high-quality green teas actually contain more caffeine than average. Tea's caffeine content isn't up to the processing methods (i.e. the category), but rather genetic and growing factors, and especially the kinds of leaves picked: buds or tip leaves contain the most caffeine, and the caffeine concentration decreases as you get to the lower, bigger leaves.
It is common to see comparisons where one cup of green tea contains less caffeine than e.g. black tea, but those are based on a single infusion which is done at a lower temperature (ca. 80 °C) and for a shorter time (ca. 2 min) than a benchmark black tea (100 °C, 3–5 min). The leaves themselves don't necessarily have any less caffeine, and all good-quality leaves have enough taste (and also caffeine) for subsequent infusions which will mitigate the caffeine content differences in the first infusion.
There are a few Japanese specialty green teas that naturally have less caffeine due to their leaf composition. Those teas are bancha, made from lower/bigger leaves; genmaicha, made from bancha and roasted rice; kukicha, made from the leaves' petioles/leafstalks (a common mistake is to call them "stems"); and houjicha, made from bancha or kukicha that's roasted until brown. In any case, caffeine-sensitive people might do best to avoid tea in favor of herbal infusions close to sleeping time.
SUMMING IT UPGreen tea is a harbinger of freshness and lightness, and it's a perfect spring and summer refreshment. It's good for people in the same ways that other tea categories are. If you'd like to try some really nice green tea, our tea house and online store have a tasty selection of Chinese, Japanese and South Korean teas. Try them sometime!
Text written by Mika Hannola