There is perhaps no better way to taste a sun-ripened tomato than by slicing off a thick slab and sprinkling it with salt. This ubiquitous powdered mineral is the magic wand of the kitchen—transforming and enhancing flavor, shelf life, and even texture with a pinch here, a flick of the wrist there.
In a manner of speaking, all salt in the form we know it comes from the sea: sea salt is evaporated directly from collected sea water, while much of the world’s refined table salt comes from deposits left by ancient oceans. Salt deposits that form veins in the rock are extracted though shaft mining and the resulting salts are mainly used for icy roads and agriculture. Salt beds—wider underground deposits—are extracted using solution mining, where water is pumped underground to dissolve the salt, then pumped back out and re-separated in a salt evaporation facility (most table salt is manufactured this way).
But the ocean isn’t the origin of salt, merely its concentrator. Like an enormous caldron, the ocean collects minerals eroded by rainwater from rocks on the earth’s surface, which is transported to the ocean by rivers or underwater hydrothermal vents. As ocean water evaporates, it leaves minerals like sodium chloride behind, where they concentrate. Ocean dwelling creatures use some of these minerals, such as crustaceans that need calcium for their exoskeletons or diatoms that need silica for their shells. Other minerals, mainly sodium and chloride (which constitute 85% of the dissolved minerals in sea water), appear to go unused.
Fresh water carries sodium chloride from earth to ocean, and so it contains trace amounts of salt itself. Plants also extract sodium chloride from soil deposits, though the quantity is functionally insignificant for human dietary needs. Animal meat contains slightly higher amounts of salt than vegetables, as their bodies’ cells, like our own, depend on sodium to maintain proper fluid balance, as well as nerve and muscle function.
Though diets of primarily animal protein may have provided sufficient sodium to early humans, hunter-gatherers and agrarian people alike began supplementing their diet with harvested salt as long as 10,000 years ago. The ocean was the easiest and best source, and salt was a valuable commodity for millennia of local and global trade. Inland salt could be collected at salt springs; one of the oldest known salt extraction sites is located in Romania next to a mineral spring with high salt content, a production that began around 6,050 BC.
Modern day refined salt has little in common with these ancient extractions. The refining process results in stripped down sodium chloride further treated with additives like iodine and anti-caking agents. Because all other minerals are removed, some argue, common table salt offers less nutritional benefit. Unrefined salts collected from the living sea or ancient deposits contain a vast array of subtle flavors imbued by the environment from which they are extracted—hence briny or even vegetal sea salts.
Traditional salt evaporation methods also lend salt a wide range of textures—from large, heavy crystals that sink like granules of sand to the bottom of the saltpan, to the light, crystalline flakes of salt that form near the surface. Fleur de sel, or flake salt, are the product of this former method, resulting in what is known as a finishing salt—flakes whose tender, airy crunch adds an ethereal quality to a bowl of dressed salad greens or a plate of roasted vegetables.
Salt is one of the five tastes our tongue can perceive—an appointment that seems to betray its importance in our development and well being as a species. And salt (from any source) makes food taste better by masking bitter, metallic, or chemical flavors (and therefore enhancing the perception of sweetness), balancing and concentrating flavor, and creating a perception of thickness or fullness (especially in sauces and soups). We crave not just its inherent saltiness, but also the transformative power it has on the foods we require for all other forms of nutrition.
To me, summer is the time of salt and its subtleness—to enliven garden vegetables and to make the brines that will preserve them for winter. Pinch with a light but steady hand.