Salt is the alpha and omega of the kitchen. This edible mineral, sodium chloride, is essential for our survival, and so we are prepared to identify its presence in food as something pleasant. Salt is one of the basic flavours detected by the taste buds, but salt is also the condiment par excellence, and, as Chef Samin Nosrat says in her book Salt, Fat, Acid, Heat, "The right amount of salt causes a 'ding!' that makes us exclaim 'how good!' No matter how technical, whoever doesn't master the touch of salt will never triumph in the kitchen." In Nosrat's words, "used properly, salt dampens bitterness, balances sweetness and enhances aromas".
In nature, salt is found on land in surface salt flats, springs or rock seams at medium depths, or in the sea. Humans have learned to procure it since ancient times. In China, salt was being extracted 29,000 years ago. Salt travelled along the first trade routes as a precious product with currency value and today, although common salt is ubiquitous and cheap, some special rock salts from underground springs, or sea salts of artisan production, reach high prices and give a special touch to all types of dishes.
Another characteristic that has made it very valuable is its use as a preservative, born of its special relationship with water. "Sodium chloride dissolves in water in individual atoms that are smaller and more mobile than any other molecule, and that is why it penetrates quickly into food," explains Harold Mc Gee in Cooking and Food. The attraction between water and salt helps to extract water from food by osmosis in preserving by salting, where a large amount of salt deposited on the surface of a solid piece of food draws out the water from the inside, preventing the process of putrefaction, which needs water, and with the advantage that the abundance of salt prevents the development of bacteria and microorganisms.
Salt also degrades the fibres responsible for muscle tone in meat, transforming them into gel on contact. That is why the previous soaking of meats such as chicken or pork in marinades or brines is a way to make them more tender. The immersion or injection of brine is a fundamental process in the preparation of cooked ham or bacon.
In pickling and fermenting vegetables and fruit brine, besides favouring the development of lactic bacteria and inhibiting putrefaction, it helps to preserve the crunchy texture of vegetables.
Generally speaking, using salt well in the kitchen is a matter of tasting and salting at the right time and choosing the type of salt for each food. In general to use salt in the kitchen you don't need to invest a fortune but a quality sea salt costs a few cents more and provides nutrients that have been eliminated in the table salt process. In terms of time, add salt from the beginning in vegetable cooking, where it will help to preserve firmness and colour, and in the cooking water of legumes (try adding salt when soaking them, it does not harden them and makes them tastier). The water to cook pasta and rice should be salted over what seems prudent, and a pinch of salt added at the start of sauteeing onion or peppers helps to soften them.
When cooking vegetables with a tendency to be bitter, such as aubergines, pre-salting (at least half an hour) helps to eliminate bitterness. Tomatoes also improve flavour if salted for a while before finishing the salad dressing. Salads with leafy vegetables, on the other hand, will wilt if salted too early.