Whether you're preparing a dinner of fried catfish and succotash or chicken Kiev and asparagus, the same scientific rules apply. For example:
During deep frying, moisture released from the food hits the oil and creates steam. Once the moisture is gone and steam stops pushing fat away, the food sucks up more fat.
Thus, the size, cut and moisture content of the food being fried determines how greasy it will be. Shoestring potatoes, for instance, have less moisture than steak-cut fries and will absorb more fat.
For breaded fried food, the size of bread crumbs determines how much oil is absorbed. Large bread crumbs and batters with sugar or fat absorb more oil than fine bread crumbs.
Thus, the finer the batter or coating, the more delicate the food.
Steaming vegetables whenever possible and cooking them for as short a time as possible will cut down on color and flavor loss. Or, cook in salted water that is already boiling; the already boiling water cuts down the cooking time, and the salt reduces flavor loss.
As vegetables with high sugar content -- such as corn, beets and carrots -- mature, they become more fibrous and the sugar begins to turn to starch. The loss of sweetness in mature vegetables can be offset by adding a little sugar to the cooking liquid.
Green vegetables should always be cooked uncovered. If the acids that are released during heating are trapped by a lid, the green vegetables turn gray.
White and red vegetables can be cooked with the lid on. They like the acids. In fact, to keep white vegetables a creamy color, add a little bit of lemon juice to the cooking water. Red vegetables, such as red cabbage, act as a kind of litmus paper and turn brighter when vinegar is added to the pot. If acid is not added, the cooking liquid will turn blue.
To demonstrate this, put some red cabbage in two clear glasses of water, and add vinegar to just one of the glasses.