Buying, storing and cooking eggplant

When buying eggplant, look for firm, purple to purple-black or unblemished white eggplants that are heavy for their size. Avoid withered, soft, bruised, or damaged eggplants. Withered eggplants will be bitter and damaged ones will be dark inside. Handle eggplants carefully. If you bruise an eggplant, its damaged cells will release polyphenoloxidase, an enzyme that hastens the oxidation of phenols in the eggplant's flesh, producing brown compounds that darken the vegetable. Refrigerate fresh eggplant to keep it from losing moisture and wilting. During preparation, do not slice or peel an eggplant until you are ready to use it, since the polyphenoloxidase in the eggplant will begin to convert phenols to brown compounds as soon as you tear the vegetable's cells. You can slow this chemical reaction (but not stop it completely) by soaking sliced eggplant in ice water—which will reduce the eggplant's already slim supply of water-soluble vitamin C and B vitamins—or by painting the slices with a solution of lemon juice or vinegar. To remove the liquid that can make a cooked eggplant taste bitter, slice the eggplant, salt the slices, pile them on a plate, and put a second plate on top to weight the slices down. Discard the liquid that results. A fresh eggplant's cells are full of air that escapes when you heat the vegetable. If you cook an eggplant with oil, the empty cells will soak it up. Eventually, however, the cell walls will collapse and the oil will leak out, which is why eggplant parmigiana often seems to be served in a pool of olive oil. Eggplant should never be cooked in an aluminum pot, which will discolor the eggplant. If you cook the eggplant in its skin, adding lemon juice or vinegar to the dish will turn the skin, which is colored with red anthocyanin pigments, a deeper red-purple. Red anthocyanin pigments get redder in acids and turn bluish in basic (alkaline) solutions.