The Real Reason You Should Never Skip Salt When Cooking Onions
Salt is the greatest, simplest, most affordable flavor enhancer in existence. Adding just a bit of it to your food makes a world of difference: it changes your pasta water, your soup, your butter, and even your baked goods with its magical touch. Any good chef understands the importance of seasoning; and many celebrity chefs — including Gordon Ramsay — have quite a thing for salt (per YouTube). Knowing how to salt something properly without overdoing it is an important skill. In fact, salt is arguably the most important seasoning in the world.
But salt isn't just for seasoning. Salt (NaCl) does a whole host of other things due to its chemical structure (per Fine Cooking). Adding salt to water actually lowers the temperature at which it freezes (which is why it's used on highways in the winter). Salt has been used for hundreds of years as a preservative because it impedes the growth of undesirable microbes in food by drawing out the moisture those microbes need to survive. While salt isn't the go-to method of food preservation it once was, salt preservation is still used for many foods — including jerky, ham, dry-aged steaks and pickled vegetables (via Delishably).
Salt isn't just for flavor
That same principle is what makes the key difference when cooking onions. Sure, you add salt to your onions to make them taste better. But the key reason you should salt your onions is to improve their texture and consistency. When you salt onions, you draw water out of them, breaking them down and browning them faster (per My Parisian Kitchen). This means your onions wilt sooner, getting smoother and creamier more quickly. That's always desirable when cooking onions, but especially so when caramelizing them. Adding salt both speeds up the process and makes the final result denser and jammier (via Splendid Table). Since the salt draws water out of the onions as they cook, you also need less butter and oil to get them to the dense consistency that makes caramelized onions such a glorious addition to so many foods.
The best practice is to add salt at the beginning of the process. This is true in general, but especially with onions, since you can then make use of both the time and flavor boost of the salt. This neat trick applies to other alliums as well. Gordon Ramsay salts his garlic before mincing, which both softens the flavor and helps it cook better, according to Tasting Table.
Never underestimate the power of salt. After all, what other rock does so much, so often, for so little?