What is the difference between sour and bitter?

If you are not sure what bitter tastes like, start with some turmeric from the spice rack, or make some strong yarrow tea, which is mildly bitter. Graduate to some goldenseal or boneset tea to really get a hit of bitter. Or try some Swedish bitters before a meal to stimulate digestion. Then compare the flavour of straight cranberry, and you will know the difference between sour and bitter. Sour makes your cheeks pucker, while bitter hits the back of the tongue in a very satisfying way.

The main difference between sour and bitter is that sour things, like lemons, pickles, or vinegar, have an acidic pH. Things that are bitter, like chocolate powder, have a basic pH.