If you are provided with some vegetables to cook, you generally add salt into the vegetables during cooking process. After adding salt, vegetables release water. What mechanism is responsible for this?

The mechanism responsible for water release from vegetables when salt is added is exosmosis, a specific type of osmosis where water moves out of cells into the surrounding environment. When salt is sprinkled on vegetables, it creates a hypertonic solution on the vegetable surface—the salt concentration outside the cells is much higher than the concentration of dissolved substances inside the vegetable cells. Following osmotic principles, water moves from the area of lower solute concentration (inside the vegetable cells) to the area of higher solute concentration (the salty environment outside), crossing the semi-permeable cell membrane.

As water exits the cells, the vegetable cells lose their turgor pressure (the pressure of water against the cell wall that keeps cells firm), causing them to become flaccid and the overall vegetable tissue to wilt and shrink. This process is visible as droplets of water appearing on the surface of salted vegetables and the vegetables appearing softer and reduced in volume. This principle is deliberately used in cooking to remove excess water from vegetables like eggplant, cucumber, or cabbage before further preparation, which concentrates flavors, improves texture, and prevents dishes from becoming watery. The same mechanism explains why salted vegetables in pickles remain preserved—the high salt concentration prevents microbial growth by drawing water out of bacterial cells as well.