Beneath the surface of Hutchinson, Kansas, and thousands of square miles of its environs lies an enormous deposit of a precious rock-like mineral called halite. There, several huge mining operations extract almost 1 million tons per year, and that’s less than one-half percent of the world’s annual halite production.
What do we do with all that halite? Among other things, we eat it; it is the only natural rock consumed by humans. The other name for this crystalline mineral is rock salt. And unlike the crystals that some people carry around for their supposed healing powers, this is one crystal that really does keep us alive and healthy.
Common salt, sodium chloride, is probably our most precious food. Not only are its sodium and chloride parts (Techspeak: ions) nutrients that we can’t live without, but saltiness is one of our fundamental taste sensations. In addition to its own flavor, salt has the seemingly magical ability to enhance other flavors.
The word salt doesn’t describe a single substance. In chemistry, it is a generic term for a whole family of chemicals. (Techspeak: A salt is the product of reaction between an acid and a base. Sodium chloride, for example, results from the reaction of hydrochloric acid with the base sodium hydroxide.)
Some other salts of gastronomical importance are potassium chloride, used as a salt substitute in low-sodium diets; potassium iodide, added to common salt to supply iodine in the diet; and sodium nitrate and sodium nitrite, used in curing meats. Unless I indicate otherwise, I’ll do what everyone else does outside of the chemistry lab: use the word salt to mean sodium chloride.
In the face of so many different salts, can what we call “salty” really be the unique flavor of sodium chloride? Undoubtedly not. Taste one of the potassium chloride “salt substitutes” and you’ll describe it as salty, but it’s a different saltiness from the familiar flavor of sodium chloride, just as the sensation of sweetness is slightly different among different sugars and artificial sweeteners.
In addition to its roles as a nutrient and a condiment, salt has been used for thousands of years to preserve meats, fish and vegetables for consumption long after the hunt or the harvest was over.
While I can’t solve the mysteries of salt’s nutritional or savory qualities, I can tell you about the physical and chemical roles it plays in our foods, including preservation.