Manufacturing of fine tea is nothing less than an art. There are endless variables a tea maker has to consider at every step. The impact of sunlight is one among many variables, and the “o-oi-shi-ta” technique practiced in Japan brings it to sharp focus.
While manufacturing high end teas like ceremonial matcha, gyokuro and kabusecha the entire field of tea bushes is covered with a thick layer of straw or a dark nylon screen to block the sunlight for 2-3 weeks before the plucking. This is called o-oi-shi-ta which literally means under a cover.
Image courtesy www.matchaorganictea.com
Japanese tea experts believe that tea grown under such intense shade has increased levels of chlorophyll that results in intense green leaves (in the case of Gyokuro) and brothy, emerald-colored brew in the case of matcha. It also leads to a higher concentration of amino acids, especially L-theanine that is said to bring about the "umami" flavor in the tea.
Umami is a kind of "savoriness", which Japanese believe to be the "fifth" taste sensation besides sweetness, bitterness, saltiness and sour. It is a desirable attribute.
Image courtesy greenteachronicle.com
In other traditional tea growing regions, importance is placed upon “shade trees” being grown in tea plantations. However, the method and motivations are very different than the ones found in Japan.
In other countries trees are grown amid the tea gardens for nitrogen fixation, soil conservation, moisture retention, manurial effect from fallen leaves, and even for pest control. The shade provided by the trees are considered essential to block the intense summer sun where the ambient temperatures can reach over 90F.
Image courtesy 2bp.blogspot.com
Although the impact of shade trees on the taste of tea is not directly acknowledged in conventional tea gardens, one study claims that tea grown in shade “to have a lower quantity of catechins (resulting in a less astringent beverage) and increased levels of carotenoids and chlorophyll (which may assist in aroma production).”
The suggestion that catechins and not chlorophyll causes bitterness in tea is interesting. Although it might be desirable to diminish bitterness in tea, could the reduction of catechins, however, mean lessening the beneficial properties in tea? Or, is the abundance of amino acid in high-grade teas like matcha and gyokuro compensate for the catechins loss?
Interestingly, while looking into the health benefits of chlorophyll we discovered a plethora of chlorophyll-based “health supplements” in the market. Apparently, chlorophyll alone has its own tall list of health claims!