What's the role of salt in cooking? Is it important to add it at certain times? Most recipes (and culinary schools) advise seasoning food with salt early in the cooking process, not just at the end. We decided to investigate this conventional wisdom to see if the timing of seasoning makes a notable difference.
We roasted carrots and prepared beef stew in two ways: For one batch we seasoned the dishes at the very beginning of cooking and, in the case of the beef stew, also when we added the onions. For the other batch we withheld all the measured salt in the recipes and added it at the end.
The roasted carrot samples were drastically different from one another. Those seasoned before roasting, with 1½ teaspoons of salt, were properly seasoned and flavorful throughout. Meanwhile, the carrots seasoned with the same amount after roasting were seasoned only on their exteriors and also tasted far too salty.
When it came to the beef stew, when we salted the meat before cooking (with 1½ teaspoons of salt) and seasoned the onions (with ½ teaspoon of salt) when they went into the pot as directed, the stew and particularly the meat itself were more evenly and deeply seasoned than those in the sample salted only at the finish. Furthermore, as with the carrots, the stew's gravy tasted far too salty when the salt was added at the end.
We know that salt penetrates food slowly when cold. (In a previous experiment, we found that it took 24 hours for salt to diffuse into the center of a refrigerated raw turkey.) While the process is faster during cooking—for example, our science editor noted that the rate of diffusion of salt into meat will double with every 10-degree increase up to the boiling point—it's still not instantaneous. Furthermore, salt penetrates vegetables even more slowly than it does meat (this is because the salt must cross two rigid walls surrounding every plant cell, while the cells in meat contain only one thin wall). Adding salt at the beginning of cooking gives it time to migrate into the pieces of food, seasoning them throughout. Meanwhile, if you add salt only at the end, it provides a more concentrated, superficial coating that immediately hits your tongue.
For the most even seasoning and well-rounded flavor, we strongly encourage seasoning foods early in the cooking process as we direct in our recipes. However, if you forget, do not make up for it by simply stirring it all in at the end. Instead, start with a very small amount of salt—we used a mere 8 percent of the original amount of salt for the carrots after roasting (⅛ teaspoon versus 1½ teaspoons) and 31 percent for the beef stew (just over ½ teaspoon versus 2 teaspoons)—and then taste and season further as desired. On the flip side, if you are watching your salt intake, you could wait until the end of cooking to season your food, knowing that you'll be able to get away with a lesser amount.
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