Why Tea Changes Its Flavor Depending On Water Temperature?

What temperature do you use to brew your teas? Do you have a preferable water temperature for your favorite teas? Today, I'd like to share what exactly happens to your tea when you change the water temperature.

There are 3 kinds of major components related to the flavor of tea - Caffeine, Tannin, and Amino Acid. Caffeine has bitterness, Tannin has astringency, and Amino Acid has sweetness or Umami. Each component has different resolution rate depending on water temperature. See the chart below.

As you see, Caffeine and Tannin dramatically change their resolution rate depending on water temperature. The higher the water temperature is, the quicker the components are extracted. In other words, they were not extracted well into low-temperature water.
On the other hand, Amino Acid doesn't change its dissolution rate regardless of water temperature. Even into the 104F water, more than 60% of Amino Acid are extracted in 4 minutes.

This is why many tea companies recommend to use low-temperature water for Sen Cha or Gyokuro which have nice sweet flavor. If you use high temperature for these teas, bitterness and astringency overpower the sweetness, and you cannot enjoy their authentic flavor.

Also, this is why you need to steep longer when you use low-temperature water. With 104F water,  bitterness and astringency are not extracted well even after 4 minutes, but sweetness/Umami is extracted according to the steeping duration. By steeping long time with low-temperature water, your tea will be full-body sweetness/Umami.

Hope this information will be of help to you.