Tannins are natural compounds found in plants—think grape skins, tea leaves, and even bark. They’re the reason red wine dries out your mouth and why a good black tea feels so satisfyingly crisp. And yes, they are acidic little molecules that can drop the pH level of whatever they’re in.
How Tannins Pull the pH Levers
When you steep a bag of black tea in water, those tannins dissolve and release hydrogen ions. More hydrogen ions = lower pH, meaning your tea becomes slightly more acidic. It’s like a tiny chemistry party in your cup, and tannins are the guests who bring the sour punch.
But here’s the kicker: the effect is mild. A cup of tea typically has a pH between 4.9 and 5.5, which is about as acidic as a tomato. So no, you’re not brewing battery acid—just a gentle shift that adds complexity.
