Today I would like to talk about how the taste of green tea changes as a result of several brewing. The following numbers express the difference between amino acid (umami) and tannin (bitterness) contents which are produced on each brewing. (deep-steamed sencha)
First brewing: 0.45
Second brewing: 0.28
Third brewing: 0.21
Fourth brewing: 0.17
Fifth brewing: 0.15
The abovementioned numbers are obtained by dividing the proportion of amino acid by the ratio of tannin (amino acid / tannin = n) as shown in the example below:
Example: First brewing - Amino acid 63mg, Tannin 140mg, 63/140 = 0.45
(The data is from Nihoncha adviser Kouza dai2kan)
Hence, you can find umami in the earlier brewing. You taste more bitterness and less umami in later-brewed tea. A lot of umami substance is extracted in the earlier brewing. Bitterness infuses constantly to the later brewing. By the third brewing 78% of umami and 43% of bitterness in the leaves extracted out. By the fifth brewing, 97% of umami and about 63% of bitterness is extracted from the leaves.
You can enjoy the change of the taste on each brewing. That is one of the charms of Japanese tea. You enjoy umami in the green tea flavor on the early brewing. As you brew the tea some more, umami is gone and you can enjoy the refreshing taste with bitterness on the late brewing. Have fun!