Cold brew tea is so cool and trendy!!
Now June is the month for iced tea in USA. In Japan, cold brew tea is also gaining interest.
As described at the past post, where Japanese tea instructor explained how to use the filter-in bottle, cold brew tea is easily prepared by using “filter-in bottle”, which is the glass bottle with silicon rim including a detachable filter inside.
Desired amount of loose leaf tea should be steeped in the filter-in bottle depending on our preference. Loving denser taste as I do, I often put 10-20g tea leaves into the bottle.
We can infuse loose leaf tea using a normal tea pot. Almost everyday, I steep loose leaf tea using Kyusu tea pot and put the Kyusu in the refrigerator before going bed. This method provides me with perfectly infused cold brew tea. Approx. 6 hours steeping extract rich umami and proper amount of caffeine, which is enough to make me motivated to work. As well as a cup of morning coffee gives us a power as described by Hemingway, a cup of morning tea is also good for our body and give a power for each day.
If you bring cold brew tea for one-day trip, I’d like to recommend a method of ice steeping in a thermos as described below.
(1) Put a tea bag in a thermos
(2) Put some pieces of ice into the thermos
(3) Fill mineral water in it
We can adjust the degree of steeping and coldness by changing the amount of ice. If it will take approx. one hour for the destination, I often put 1 or 2 pieces of ice, which equals to 50 to 100ml of ice. If it will take approx. 4-5 hours for the destination, I put 3 or 4 pieces of ice, which equals approx. 150 to 200ml. (In this case, the volume of ice is approx. 50ml I use.)
In addition, I control the concentration of tea constituent by adjusting the amount of loose leaf tea. Using disposable filter bag is convenient to adjust the input amount of loose leaf tea.
From the viewpoint of science, cold brew tea has a beneficial effect derived from higher extraction of epigallocatechin(EGC) relative to epigallocatechin gallate(EGCG).
EGCG has various benefits for our health. As for the effect for mucosal immune system, however, EGCG suppresses the production of IgA. On the other hand, EGC can activate the IgA production.
When brewing tea, EGC and EGCG can be released from tea leaves at the same time. Interestingly, the extraction behaviors of EGC is different from that of EGCG, depending on the temperature. EGC can be extracted more than EGCG under lower temperature. Oppositely, EGCG is extracted more than EGC at higher temperature, as shown in the below.
Thus the cold brew provides the lower ratio of EGCG/ECG, resulting in higher IgA production, which means the activation of mucosal immune system.
In other word, cold brew tea could help the defense system of our bodies against pathogen infection.
In summer time, let’s enjoy hot activities with cold brew teas!
< Reference >
[353] Monobe N., Ema K., Tokuda Y., Maeda-Yamada M. (2010) : Effect on the Epigallocatechin Gallate/Epgallocatechin Ratio in a Green Tea (Camellia Sinensis L.) Extract of Different Extraction Temperatures and Its Effect on IgA Production in Mice, Bioscience Biotechnology and Biochemistry, 74(21):2501-2503.