The different categories of teas are broken down by how much they are oxidized and processed. White teas, yellow teas and green teas are unoxidized, while oolong, red tea and black tea are either partially or fully oxidized teas. As a tea is oxidized, its leaves turn a darker color and the liquor of the tea becomes darker as well.
Green teas are heated after being harvested. This heat deactivates the enzymes that cause oxidation so instead of oxidizing over time and turning into a black tea or an oolong tea, the leaves stay green. The leaves also retain more of their natural flavors, so green teas tend to take on a fresher more vegetal taste and aroma. When a tea is oxidized and turned into a black tea, these flavors are converted into warmer notes like caramel and honey.
The method of processing green teas can vary based on the country it is produced in. In China, it is more common to heat the teas in a large pan, giving these teas a slightly more floral flavor profile. In Japan, it is more common to steam the tea leaves, giving Japanese green teas more of these steamed vegetable or even seaweed notes.
While most Japanese green teas are steamed, Kamairicha (right) is actually produced with the Chinese pan-firing method. This allows the tea to inherit some slightly warmer notes of cashew nut and caramel. This tea is very rare in Japan as a whole, but in the prefecture of Miyazaki, there are many talented farmers like Mr. Issin (left) that produce tea using this style.
Certain Sencha teas can be steamed for a longer time to produce Fukamushi or deep steamed teas. These teas are steamed for just an additional 30 seconds, and during that time the cell membranes of the tea are broken down just a little bit more. This allows the leaves to break down more easily and allows the water to extract more from the leaves. This is why you see Fukamushi teas taking on this beautiful Jade green color, particularly the second time you brew them.
Because green teas are unoxidized, they are more sensitive to temperature. Japanese green teas should be prepared between 140-170 degrees Fahrenheit, otherwise the water will bring out too much of the bitterness. During the oxidation process, the tea loses a lot of its flavanols, so black teas don’t encounter this problem as much.
Another benefit of green teas is that they work great as a cold brew. The cold water extracts these more sweet and fruity notes from the tea and less of the bitterness. A cold brewed green tea can be a great refreshing drink to enjoy on a warm afternoon. All you have to do is add 5 grams of leaves to a pitcher, pour in 500ml of room temperature water and let it brew overnight. In the morning you will have a smooth, refreshing cold brewed tea!