Eggplant is often considered to be very bitter. One of the secrets chefs use to remove the bitterness is to coat the surface of the eggplant with salt. As the eggplant sits, it becomes wet and when the wetness is rinsed or wiped away the bitterness is gone. Explain what is happening to improve the flavor of the eggplant.

Imagine the skin of an eggplant. It is more than just a protective layer; it's what we describe as a semi-permeable membrane. This means that while it blocks certain substances from passing through, it allows others, like water, to move freely. In the kitchen, this characteristic is harnessed during food preparation.

When salt is sprinkled onto the surface of an eggplant, the semi-permeable nature of the skin comes into play. Water within the eggplant begins to move out towards the area where the salt concentration is higher, demonstrating the remarkable process of osmosis. This movement is selective; the membrane permits water to pass but retains most other substances inside the eggplant, including some that contribute to its bitter taste.

Understanding solute concentration is key to mastering culinary techniques like the reduction of bitterness in eggplants. By salting the eggplant, chefs take advantage of the concept that water naturally moves from a region of lower solute concentration—the inside of the eggplant—to a higher solute concentration—the salted surface.

Solutes are substances like salt or sugar that dissolve in solvents such as water. The interaction between solute and solvent on each side of the eggplant skin generates a concentration gradient. It's this gradient that provides the driving force for osmosis. Chefs exploit this scientific principle, effectively drawing out water and with it, some of the bitter tastes, thus improving the eggplant's flavor.

Eggplants contain natural substances that can taste quite bitter to some people. These compounds, which are often water-soluble, can be reduced effectively through osmosis. The action of osmosis, induced by the salt, doesn't just remove water from the eggplant; it also pulls out these bitter compounds.

As osmosis continues due to the presence of salt, the bitter-tasting soluble substances are carried away within the water that escapes through the eggplant's semi-permeable skin. The subsequent step of rinsing removes any remaining salt and the water that contains the bitterness, resulting in a more palatable vegetable.