Have you wondered why the cooking directions for frozen food say to boil the water before placing the vegetables in the pan? Here’s why. Water contains some air. When it is heated, this air is driven off. If the food is placed
in the water before the air has been eliminated, some of the vitamins that dissolve in water, especially vitamin A, are carried off with the air as the water approaches the boiling point.
So boil the water before you cook frozen or fresh foods in it. Use a small amount of water for most foods, only as much as is necessary to steam them tender. A container with a tight lid is always the most satisfactory. If you don’t have such a container, put a heaven object on the lid to prevent it from lifting and letting out the steam.
After putting the frozen or fresh food into the boiling water, bring it to a boil as fast as possible le. Then reduce the heat so that it simmers, and do not lift the lid until you are fairly sure the food is cooked. Avoid stirring vegetables and fruits during cooking as this mixes air in again and will cause loss of more vitamins during the rest of the cooking period.
Re heating any leftover food destroys even more vitamins, especially vitamin A, so try not to cook any more than will be used at one meal. If food is left over, it can be used in healthful salads instead of being thrown into the garbage can.