By now, most of us with an interest in gastronomy have experimented with or at least heard of the technique known as brining. This is a subject that tends to be more widely discussed during the holidays, since the process is especially useful for large meat items that require extended cooking times (like turkey) and for preserving meats (like cured ham). The active ingredient at play is, of course, salt, specifically sodium chloride. It is probably the least exotic-which is to say that it is the most commonly used, most ancient, and most useful-seasoning on earth. Unlike nearly everything else we use for cooking (utensils aside), it is inorganic: Because it naturally occurs in its crystalline form, it is a mineral, a rock straight from the earth, unlike sugar, which is produced naturally only in living organisms. We need it to survive, yet too much is very damaging, even deadly. And although most of the salt that's produced in the world is used for things other than human consumption, it really does make food taste better. Like, for real it does, because, duh, science. CliffsNotes on how we taste things vis-a-vis neurophysiology, comin' in hot. . . .
We sense things electrically, via tiny changes in current. The cells in our taste buds operate at a constant negative voltage. There's a buffer zone of plus or minus a bit of voltage where nothing really happens, but when that base voltage is raised to a certain level, it's like you flip a switch and bang, your brain is alerted to the fact something is happening. This is called an action potential, and when food does this, we taste it. Well, salt that's been dissolved in water (or saliva) acts to raise that base voltage level a few ticks so those cells operate at a voltage that's closer to the switching point, aka the threshold stimulus. Basically we are physiologically more sensitive to the thing we know as flavor when salt (in solution) is on our tongues. But, of course, if there's too much salt, our brains are overwhelmed with "this is salty" signals. The salt must be dissolved to be effective at this due to ions and shit, which is why the idea that "adding salt before you eat is the same as cooking with it" is just dumb. Undissolved surface salt will hit your tongue and overload it, whereas already dissolved salt will be way better at priming them up for other incoming chemicals. Anyway, this extra sensitivity is also a reason why it hurts to get salt in a cut, what with all the exposed nerve cells and such. So I guess rather than making food taste better, salt, more accurately, makes us able to taste food better.
Except that salt also suppresses our ability to sense bitterness. This is why pairing salt with chocolate and certain vegetables like cabbage or bitter greens is pleasant and sometimes even necessary. So really both wordings can be considered valid. Also, salting the surface of meats, for instance, draws out flavor and aroma compounds so they hit our tongues first, in addition to facilitating the all-important Maillard reaction, again enhancing taste. Also, brining breaks down and affects muscle tissues in a way that enhances both tenderness and moisture retention. Lastly, certain enzymes in saliva that serve to convert starches into sugars are activated by the component ions of salt. Long story short, salt kicks ass at cooking.
Types of salt
Table salt: Fairly fine cubic crystals of pure sodium chloride are good for dissolving in water and OK for adding to finished food; also good for precise measurement, and often iodized, which is good for health but which some say imparts off flavor.
Kosher salt: Slightly larger crystals make it easier to distribute with one's fingers and the difference in volume makes it about a third less salty than table salt; also, it's pure sodium chloride and never has iodine.
Sea salt: Obtained from evaporating seawater, it usually has residual organic components from algae as well as trace minerals, which contribute flavor and aroma; crystals range from light and delicate to very coarse and dense.
Fleur de sel: The lightest crystals of sea salt, often with hollow crystal structures, making it delicate in texture and flavor; used as a finishing condiment.
Gray salt: Also evaporated sea salt, its color owes to sedimentary particles that have sunk to the bottom layers, from which it's harvested.
Pink salt (often "Himalayan"): Salt with iron oxide (rust) particles that make it appear pinkish.
Black Salt: Sea salt that has been combined with a dark mineral, usually lava or clay, to make it look black.
Things to do with salt
Dry brine poultry: Much simpler and arguably more effective than wet brining, which involves submerging something in a salt solution, all this is is generously salting meat and letting it sit for a while. For a large chicken or turkey, generously salt both the surface of the skin and underneath, as well as the inside of the cavity. Let the bird sit for at least a day and up to two, then rinse off any unabsorbed salt. Pat dry before cooking and proceed as usual.
Suppress bitterness: Add a pinch of salt to any recipe calling for chocolate, especially dark chocolate. Also, adding a pinch of salt to a cup of crappy coffee will significantly smooth it out via the same mechanisms. Salting cut eggplant is traditionally considered to be a way to draw out the bitterness, and, yes, salt does dampen the bitterness. But it's also helpful in breaking down the spongy texture of eggplant, making it less likely to get overly greasy during frying.
Affect proteins and moisture content: Add a tiny pinch of salt to cream or egg whites before whipping to make the process quicker. Add salt to ground meat before mixing to make it more cohesive in a meatball or burger. Salt fish and allow to stand for about 15 minutes to remove funky smells and to enhance browning during cooking. Toss shredded or julienned cabbage, carrots, zucchini, or cucumbers with a bit of salt, and allow to sit for about a half-hour to extract moisture and break down cell walls, thereby cooking the vegetables without heat.
Enhance sweet things: Very lightly sprinkle salt on sweet, moist fruits like melons and cut peaches, and allow to stand for a minute before eating. This also works on ice cream.