It would be nice if there were salting rules. But when it comes to the question of when to salt, “there are no universally accepted, scientifically validated answers,” says Robert L. Wolke, author of What Einstein Told His Cook: Kitchen Science Explained. So instead of giving us one rule, the experts we consulted advised us to consider what we’re cooking and what outcome we’re looking for.
For example, if you’re sweating vegetables, you should add salt intermittently to help leech out the moisture, says Lauren Martey, a research and development chef for Diamond Crystal Salt. But if you’re caramelizing onions or browning mushrooms you don’t want to draw out moisture, for a better caramelization of the sugars, so you should wait until the end to salt.
Proponents of intermittent salting often feel that if they salt something like a sauce or soup along the way, they can layer flavors into it. This is possible, says Morton Satin, director of technical and regulatory affairs at the Salt Institute, but you have to prevent the natural tendency of the salt to redistribute evenly throughout the liquid. He says that if, for example, you’re making a tomato-meat sauce for spaghetti and you want to have a layering effect where you can differentiate between the saltiness of the meat and the tomato sauce, “the cooked, salted meat would be added to the tomato sauce near the very end of the cooking just to incorporate it fully but not to allow too much diffusion to take place.”
If you do salt early, be sure you don’t overdo it to avoid any unpleasant surprises later on. A slow-cooked sauce, pot roast, or pot of beans will boil off a lot of water, making the salt flavor more concentrated.