Friday, December 15, 2023

Taking tea with a grain of salt - the Boston tea party

Tomorrow is the 250th anniversary of the Boston Tea Party, the day protesting American colonists dumped 42,000 kg1 of tea into Boston Harbor. That's enough to make about 21,000,000 cups of tea. While that might sound like a lot of tea, several billion cups of tea  are drunk across the world  every day2. Each year humans drink enough tea to to fill Boston Harbor end to end. That's a bit less than half a cubic kilometer (which in those terms I confess does not sound like very much - but Boston Harbor).

The tea, once dumped in the harbor, was unusable due to contamination not only by the salt water, but by the sewage that surely polluted the bay. (I was fascinated to find that a vial of the tea leaves purportedly collected from the harbor still exists.)

Salt would seem to be the last thing you want in your tea, but in the eighth century manuscript Classic of Tea, the tea master Lu Yu recommended adding a dash of salt to water before using it to brew tea. Salt, actually the sodium ions in it, suppresses our perception of bitterness. A small amount of salt, not even enough to taste, reduces the bitterness in a cup of tea. Other ions will do this too, including zinc. Beware, zinc also interferes with the perception of sweet!

1. If you prefer this in Imperial units, that would be 92,000 pounds.
2. At this point I'm apparently contractually required to tell you that tea is the most popular beverage in the world. Virtually everything I read about tea made sure to make this point early and often.

If you want to know more about the chemistry behind tea, my book Steeped: The Chemistry of Tea comes out from the Royal Society of Chemistry Books in January 2024. You can sign up to hear me talk about the chemistry of tea on February 15 with Chemistry World.