On your tongue you possess receptors that can sense, very generally, the following tastes:
- Sweet – usually indicates energy rich nutrients
- Umami – the taste of amino acids (e.g. meat broth or aged cheese)
- Salty – allows modulating diet for electrolyte balance
- Sour – typically the taste of acids
- Bitter – allows sensing of diverse natural toxins
None of these tastes are elicited by a single chemical. What this means is that when something tastes “irony,” like water emerging from a suburban labyrinth of rusty pipes for example, we are not sensing the iron with our tongues.
The sensation of taste is actually a combination of other factors like texture and most importantly smell. When something tastes like iron you are in reality smelling the iron, which is then combined in your brain into the “taste” of something. This also happens with the other senses (which you have more than five of, by the way). Studies have shown that the color of a food will change how it tastes. For example, green french fries taste “worse” than the normal golden ones, despite the fact that the only difference is their color. Taste as a sensation is really a concatenation of various senses.