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.