Matcha is the tea used in the Japanese Tea Ceremony ("chanoyu"). It is made from the leaves of the same plant used to make black, oolong, and green tea. What makes the teas different is where they are grown (soil material), how the plant is treated, which leaves are picked, and how much oxidizing the leaves undergo after being picked.
The flowering evergreen plant, camellia sinensis, provides the leaves for tea. The small leaf variant (camillia sinensis var. sinesis) is used for matcha while the large leaf variant (camillia sinensis var. assamica) is more common in black teas. The new growth leaves begin to appear in early April. When this happens, the plant is shaded to restrict sunlight, thereby dropping the rate of photosynthesis. The plant reacts to the decreased sunlight by producing larger amounts of L-Theanine, an amino acid which gives matcha its full-bodied flavor. After the plants are shaded for about three weeks, the most tender leaves from the ends of each branch are plucked off. This first harvest of the season, known as the "first flush", is considered to be the highest grade of tea. The two most tender leaves will become koicha (thick tea), while the other tender leaves will become usucha (thin tea).
Unlike black tea, matcha is not given a chance to oxidize. Instead, it is steamed at 480 to 570 degrees F for 10 to 15 minutes to stop the oxidation process, and keep the leaves bright green. The leaves are then cooled by a gentle air dryer at 211 to 302 degrees F for 10 to 15 minutes, and spread out to dry further. When they are almost dried, the stems and veins are removed. After they are completely dried, the leaves are called "tencha".
To make matcha, producers take different tencha from different regions to blend the desired flavor. The blend of leaves are then ground to a fine powder using stone mills. The pace of milling is slow to prevent the tea from heating up and thereby changing the flavor. A typical mill will rotate once every two seconds.
Once the tencha is milled into a fine powder, it is called matcha. Matcha is ground about the same as talcum or baby powder. It is therefore sifted to break up any clumping before it is suspended in hot water to make a bowl of tea. Depending on the ratio of hot water to matcha, the resulting bowl of tea will either be thick (think very warm honey) called koicha or thin (think expresso) called usucha.
There are numerous health claims regarding matcha. Matcha contains extremely high amounts of antioxidants. The ORAC (oxygen radical absorbance capacity) value for matcha is 1440, which is more than six times that of dark chocolate (227), gokiberries (253), or pomegranate (105). Matcha's antioxidant, a flavanoid/catechin called EGCG (140 times that of brewed green tea), has been linked to a number of claims regarding prevention of dementia, increased fat burning, and more. The soluble and insoluble fibers aid in digestion. The natural sugars (polysaccharides) in matcha help stabilize blood sugar levels by minimizing insulin spikes. In addition, a rare amino acid, L-Theanine, has been found to promote relaxation and increased brain functions. L-Theanine is known to slow the metabolization of caffine which extends the wakefullness of matcha without the crash or headaches experienced from drinking coffee.