Smaller, immature eggplants are best. Full-size puffy ones may have hard seeds and can be bitter. Choose a firm, smooth-skinned eggplant that is heavy for its size; avoid those with soft or brown spots. Gently push with your thumb or forefinger. If the flesh gives slightly but then bounces back, it is ripe. If the indentation remains, it is overripe and the insides will be mushy. If there is no give, the eggplant was picked too early. Also make sure an eggplant isn't dry inside, knock on it with your knuckles. If you hear a hollow sound, don't buy it.
Eggplant should have smooth, glossy, purple black skin, free of scars and they must be firm. Soft eggplants are usually bitter. Keep cool and use eggplant in two to four days after purchase.
Never eat raw eggplant since it contains the toxin solamine. Solamine is destroyed by cooking.