I remember on my mission telling people that the reason coffee was bad was because of the tannic acid, I don’t believe that anymore, but apparently soda pop has it also.

“Use of tannic acid in food applications is far more widespread[clarification needed] and significant amounts are used as process aids in beer clarification, aroma compound in soft drinks and juices. Equally important are applications in the wine industry, where it finds use as a natural clarifying agent, colour stabilizer and taste enhancer.”