Salted_ A Manifesto on the World's Most Essential Mineral, With Recipes - Mark Bitterman [20]
Theoretically, if you filled a hundred-foot-tall cylinder with ocean water and let it evaporate, you would end up with a three-foot-thick layer of crystallized sodium chloride sandwiched between two thinner layers of other crystallized salts and trace minerals—mostly magnesium and potassium salts (which precipitate last) on the top and calcium salts (which precipitate first) on the bottom. This occurs because the different minerals in seawater crystallize at different concentrations. (This is why nearly pure sodium chloride can be mined from rock: it is taken from the massive middle layer formed by the evaporation of ancient seas.)
At a salinity of about 70 grams per liter, the first mineral to crystallize from seawater is calcium carbonate (CaCO₃), which forms limestone, chalk, and other types of rock. It is also the main component of seashells, eggshells, pearls, and over-the-counter antacids. It is followed by calcium sulfate, then sodium chloride, then magnesium sulfate. If you let the salt dry for long enough, a small amount of magnesium chloride, commonly called bittern, will develop as well. Artisan salt manufacturers tinker with, observe, adjust, and obsess over the process of evaporating salt water in order to achieve the mineral content they determine is most desirable. In Japan, they may even slow-heat the brine in order to ensure that the sodium chloride crystals take up extra bittern, which is tasty, and which they commonly believe to be beneficial to human health and well-being.
Crystallization occurs as water evaporates. At a certain point (the solubility threshold), there is not enough water to hold the salt-forming ions in solution, and they begin to bond together into crystals. This happens in two stages: primary nucleation and secondary nucleation. During primary nucleation, the first seed crystals form in a solution. When there are too few water molecules to effectively hold all of the ions, the excess ions are attracted to one another more than to the water around them and they start coming together into tiny crystals. These microscopic crystals form the seed nuclei upon which secondary nucleation builds. A brine can be gently stirred or otherwise agitated at the start of secondary nucleation to promote the development of larger salt crystals around the seed nuclei. Some salts form only when the wind gives a light ruffle to the brines they come from.
Secondary nucleation makes up the bulk of the crystallization process, and is the only part of the process that you can see happening. It can be initiated through contact with almost any solid foundation, like a seed crystal, a speck of some other material, or the side of a container. Many salt makers believe the halobacteria that live in solar salt ponds help crystal formation, attributing their purplish color (which appears red, pink, or orange in water) with trapping more of the sun’s heat and thus encouraging evaporation. Others believe the bacteria themselves may help in secondary nucleation—the salt-crystallizing equivalent of seeding clouds.
THE PHYSIOLOGY OF TASTING SALT
The role of taste is to help you separate what is good to eat from what is bad. Sweetness indicates a food that is high in energy, umami is the flavor of proteins, and our perception of salt insures that we will get the amount of electrolytes we need. Sour and bitter tastes warn us of potential harm, indicating the possible presence of toxins and contaminants in our food. Taste is just one part of our flavor-perception system—the part that’s received in the mouth through taste receptors in taste buds. Together with aroma, received through olfactory receptors deep inside the nose, and tactile sensations of texture and temperature, we get all the information we need