Hi, I've found some info about the color change of black tea based on acidity, but I would like to get some concrete answers and maybe pics of the polyphenols and tannins that are responsible for the "black" of black tea :) I'm a Chemistry student, so don't spare the details :)

At school we have been learning about metals reacting with acid.  I had a look at the periodic table and I saw that pottasium (K)  was an alkali metal.  I also knew that bananas are an excellent source of pottasium.  So why, when I eat a banana, does the hydrochloric acid in my stomach not react and make me explode?

Felix, 11, Norwich