Cut fruits and vegetables only just before cooking in order to preserve nutrients.
Cooking foods like fruits, vegetables and grains destroys some of the vitamins and minerals they contain. However, the European Food Information Council points out that most foods require at least some preparation in order for our bodies to digest them, and that cooking can actually increase the nutrient content of some items. For example, cooking reduces the vitamin C in produce like spinach or tomatoes, but significantly increases the concentration of antioxidants that may help prevent cancer. The key is to strike a balance between digestibility and nutrient content by using cooking methods that keep vitamin and mineral loss to a minimum.
Minimize Air Exposure
The U.S. Department of Agriculture cautions that the more a fruit or vegetable is exposed to air, the more vitamins will be lost, particularly B vitamins like niacin or thiamine and the vitamins A, C, E and K. To minimize vitamin loss, don't cut fruits or vegetables until just before you plan to cook or eat them, and avoid removing the peel whenever possible. Aim to chop or slice produce into large pieces rather than small ones in order to decrease the amount of surface area that will come into contact with air. If you need to prepare produce before you use it, store it in a tightly covered container.
Minimize Exposure to Water
Vegetables cooked in boiling water can lose as much as 20 percent of their vitamin content and 15 percent of their minerals, according to Consumer Reports. Yale New Haven Hospital registered dietitian Lisa Tartamella states that cleaning raw produce by presoaking or vigorous washing with lots of water can strip nutrients. Rinsing some grains, like rice, before cooking, also causes vitamin and mineral loss. To preserve nutrients, avoid boiling in favor of steaming, stir-frying, pressure cooking and microwaving. If you need to cook in water, use as small an amount as possible. After grains like pasta have finished cooking, don't rinse them since that can also wash away nutrients.
Lessen Cooking Time
Exposure to heat destroys the nutrient content of food, and especially lowers the concentration of vitamin C. Try to cook produce only until it is just tender -- avoid overcooking whenever possible. Heat pans well before sautГ©ing foods and, if you're cooking in a liquid like water, bring it to a boil before adding in produce to keep the cooking time brief. Aim to cook only as much produce as you need at one time because reheating foods exposes them to more nutrient loss.
Avoid Alkaline Cooking Liquid
Recipes for cooking green vegetables like collard greens or spinach often call for the addition of baking soda, which can help preserve the dark green color of the produce. Instructions for preparing dried beans and legumes also often include baking soda to help decrease the cooking time. Baking soda, however, causes cooking water to become alkaline, says the USDA. An alkaline cooking environment can significantly lower the vitamin C and thiamine content of foods and should be avoided.