Japanese green teas have 3 major chemical components as follows.
And here are the graphs showing how hot water temperature and infusion time influence the amount of chemical component infused to the liquid.
All Y axis unit: % infused out of each total chemical component
(Relation between Infusion Condition of Green Teas and Soluble Component, 1972, P71-74, No.37, Tea Research Journal)
Infused component ranking on hot teas １.Caffeine ２.Catechin ３.Amino acids
When you make hot tea, caffeine is the most temperature-sensitive and easiest infused into the liquid among the 3 components. Meanwhile, 20 – 60% of total catechin is infused within 2 minutes, which is the standard brewing time for Japanese green teas. Amino acids are infused as well as time goes by regardless of the water temperature. High-quality Japanese green teas contain more amino-acids in their leaves, and it is therefore recommended to use lower temperature water with longer infusion time. In addition, if you want to make less bitter, astringent, and sweeter tasting Japanese green tea, please use lower temperature water to infuse sweet amino-acids while suppressing the amount of caffeine (bitter taste) and catechin (astringent taste).
In summer, we enjoy cold Japanese teas with cold water. The following graphs explain the infused chemical component amount with cold water and longer infusion time. This experiment is also tested with standard grade Sencha.
Experiment condition: Keep in refrigerator, Test teas: bought randomly at stores in various cities
Y axis: % infused out of each total chemical component
(Effect of the Soaking Time of a Green Tea Bag in Cold Water on the Flavor and Amount of Constituent Extracted, 1999, P66, Vol.50, No.1, Journal of home economics of Japan)
Link to the source of this research papaer
Infused component ranking on cold tea １.Amino acids ２.Caffeine ３.Catechin
Amino acids are infused as time goes by. One interesting observation is caffeine is infused more than catechin with cold water, which is not the case for hot teas. And both components are infused less than with hot temperature water even after 10 hours. This means more nutrition and components remain in the tea leaves during cold infusion. If you want to enjoy the nutrition found in the tea leaves, you’d better eat the tea leaves after enjoying your cold glass of refreshing tea!
