Lettuce wilts because it loses water, so the key to reviving it is to put the water back in. We’ve had success simply soaking the wilted leaves in ice water for 30 minutes. But since water enters the lettuce’s cells through openings called stomata—and ions including hydrogen ions from acids can cause the stomata to open and take in more water—adding vinegar to the water could help crisp lettuce faster, at least in theory. As a test, we took three heads of green leaf lettuce that we’d allowed to wilt and then split each head in half and tore up the leaves (tearing created more avenues for water to enter). Half of each head went into a bowl of ice water with 2 tablespoons of cider vinegar; the others went into plain ice water.
THE BOTTOM LINE: This acid test didn’t pan out. All the samples rehydrated in the same amount of time—about 30 minutes—but the vinegar left a slight unwanted tang on the lettuce. Hydrogen ions should help the lettuce take up water, but vinegar, a rather weak acid, doesn’t have enough of them to make a difference. We’ll stick with plain ice water to refresh our salad leaves and save vinegar for the dressing.
