Salt also has some very interesting properties that impact taste indirectly. Notably, its tendency to give up some of its chemical energy as it dissolves. This happens whenever salt comes into contact with anything wet. In the mouth, it results in minute electrical charges being delivered directly to the taste buds. It’s a very minor transfer of energy, of course, but it can have a big impact on how a food tastes.
As I’ve often mentioned, it’s not just the tongue that’s involved in the human taste sense. The olfactory (smelling) sense plays a big part. However getting the sense of smell involved in tasting means the food must be volatile to some degree, i.e. it must be capable of launching some of its molecules into the air. This doesn’t just happen by itself. It takes energy. To achieve liftoff a given molecule — for example, a water molecule — needs to gain sufficient energy to overcome the forces of surface tension (the pull that molecules on the surface of a body of water exert on one another). Often it’s heat that supplies this energy, say, when water boils. But it can also be supplied chemically, which is where salt comes in. A little salt it is all that a few molecules of water need to get airborne, and when they go they frequently take other aromatic compounds that are near them, like essential oils, along for the ride. Those get into our nasal cavities and well…you know the rest.
This is why it’s possible to literally detect, solely with your nose, whether a sauce, soup or stock has been seasoned, even when it’s cold. Because it doesn’t smell like anything. But add little salt and a plain Jane unseasoned soup turns into a whole new aromatic experience.