In the tongue there are receptors for fundamental tastes like acid, bitter, salad and sweet, and this could propose several questions. What's the difference between lemon juice and water? Of course, lemon is very acid and the water seems neutral. All of this is related to pH.
If pure water has a pH of 7, it's considered nor acid nor base in chemical terms. It's easy of understand; when the pH goes lower than seven the taste starts to be acid. Lemon juice has a pH of 2'2 and that's the reason for its great acidity. Acidity looks related with problems, as the pH of the aliments is well documented and the list includes alcohol, coffee, tea, chocolate, artificial sweeteners, fruit juice with refined sugar, meat, fish, etc. Does anyone need more indications by Nature?
For reference, sea water has a pH of 8, then, is it bitter? So, any meal gains even extra complexity when every element adds its own pH.
Another curiosity that pH is also interrelated to electrochemical actions! Electricity seems ubiquitous.