But I can't resist telling you about Earl Grey tea. It's perhaps the most famous flavored tea in the West and traditionally combines a black tea with bergamot, either as peel or oil derived from the peel.
Image from Wikipedia, photo from the “Nürnbergischen Hesperidum - Volkamer”
by Johann Christoph - Nürnberg, 1714.
|Howick Hall, image from Wikipedia|
It turns out that water high in calcium limits extraction of tea leaf compounds during brewing, leading to a tea with less caffeine and less amounts of polyphenols. This effect can be modulated by the acidity of the water, with greater acidity (lower pH) leading to greater extraction and less effect of the calcium. Bergamot's acidity would thus counteract this effect of calcium carbonate.
The other effects of calcium carbonate are on the extracted brew itself. As the tea cools down, "tea cream" develops—a turbidity that dulls the shine of the tea. Another problem is that the polyphenols continue to transform, yielding a more brown-orange and less red color. Look for this color change if you add milk to tea in a glass. Both of these transformations would make the tea less attractive to people who are used to a redder tea, with or without milk.
|Black tea with and without milk—notice the color difference! Photo by Joanna Kosinska on Unsplash|
But mostly, a lower pH yields a tea that simply tastes better.
Oh, and why bergamot instead of, say, lemon, which could accomplish the same goal?
I would imagine that it is because bergamot is more fragrant—and more exotic—than lemon.
If you like your black tea better with lemon than without, now you know why.
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Yong-Quan Xu, Chun Zou, Ying Gao, Jian-Xin Chen, Fang Wang, Gen-Sheng Chen, Jun-Feng Yin. Effect of the type of brewing water on the chemical composition, sensory quality and antioxidant capacity of Chinese teas. Food Chemistry, Volume 236, 2017, Pages 142-151, ISSN 0308-8146, https://doi.org/10.1016/j.foodchem.2016.11.110.
Chandini, S. K., Jaganmohan Rao, L. and Subramanian, R. (2011), Influence of extraction conditions on polyphenols content and cream constituents in black tea extracts. International Journal of Food Science & Technology, 46: 879-886. doi:10.1111/j.1365-2621.2011.02576.x