Why do lettuce leaves become wilted after they have been in salty salad dressing for awhile?

The wilting of lettuce leaves in salty salad dressings is a result of the process called osmosis. Osmosis is the movement of water molecules from a region of lower solute concentration (higher water concentration) to a region of higher solute concentration (lower water concentration) through a semipermeable membrane.

In the case of lettuce leaves, the cell membranes of the leaves act as semipermeable membranes. When the leaves are placed in a salty salad dressing, the salt concentration in the dressing is higher than the salt concentration inside the leaf cells. This creates a concentration gradient, causing water molecules to move out of the cells and into the dressing. As a result, the lettuce leaves lose their turgidity and become limp or wilted.

The rate of wilting depends on several factors, including the salt concentration in the dressing, the temperature of the dressing, and the type of lettuce.

To prevent lettuce from wilting in salad dressing, it is recommended to use a lower salt concentration, keep the dressing cold, and choose lettuce varieties that are more resistant to wilting, such as romaine or iceberg lettuce.