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* Based on the Food Guide Pyramid from the U.S. Department of Agriculture and Human Nutrition Information Service.
With modern transportation, we can all have year-round access to a wide variety of fresh vegetables. And in our health-conscious times, vegetables are not just used as side dishes any more. Because they are economical, we can use vegetables to prepare low-cost main dishes such as vegetable primavera, stuffed squash, or vegetable lasagna. In addition to their nutritional value, vegetables make meals more appealing in flavor, texture, and color.
Cooking changes a vegetable's texture, flavor, color, and nutrient content. High temperatures make vegetables tender and enhance flavor. In addition, cooking usually makes vegetables safer to eat by killing microbes. Overcooking, however, will cause texture, flavor, color, and nutrient content to deteriorate. Herbs and spices added to vegetables must also cook long enough to extract and diffuse their flavor throughout the vegetables but not so long that flavoring will be lost. Cooking moderates the harsh flavor of onions but strengthens the odor of vegetables in the cabbage family.
The key to cooking vegetables is to make the tissue tender without making it too soft. You can determine whether a vegetable is done by testing a piece during cooking. Most vegetables should be tender but still firm. Color can also indicate whether a vegetable is done. Green vegetables are overcooked if they turn an olive green. Delicate leafy vegetables require only a few minutes to cook, while stem and root vegetables may require more time.
Consider a vegetable's appearance and texture when you select fresh produce. High-quality, fresh vegetables are young, crisp, and brightly colored. As vegetables ripen, they gradually lose flavor and nutrients and become limp, losing their crispness.
Since vegetables grow close to the ground, you may need to wash them carefully. You may also need to scrape, pare, chop, or slice some vegetables before cooking. Use carefully washed vegetable odds and ends in soups or stocks.
Store fresh vegetables for as short a time as possible to prevent loss of nutrients, flavor, and texture. Vegetables lose quality rapidly. Peas and corn begin to lose their sweetness as soon as they are picked.
Store potatoes, onions, and winter squash unwashed in a cool, dry, dark place. Refrigerate other vegetables in a covered container to prevent drying. Tightly cover vegetables that have been peeled and cut to prevent drying and discoloration.
We should eat three to five servings of vegetables every day.* A serving size usually is ½ cup of cooked vegetable or 1 cup of raw vegetable. Vegetables provide important vitamins and minerals such as vitamin A, vitamin C, riboflavin, folic acid, iron, and magnesium. Most vegetables are also good sources of fiber. They are naturally cholesterol-free and low in fat. But don't turn your naturally low-fat vegetables into high-calorie selections—try to limit the amount of butter or high-fat sauces you add to your vegetables.
Most minerals and some vitamins dissolve in water. Soaking vegetables in water before cooking or cooking vegetables in large amounts of water causes leaching of important vitamins and minerals.
The other five factors that lead to nutrient loss are high temperatures, prolonged cooking, alkalis (such as baking soda and hard water), plant enzymes (which are destroyed by heat), and oxygen. Some nutrient loss is inevitable, but most can be avoided by understanding how these six factors affect vegetables.
You should stop cooking vegetables when they become tender. Desired tenderness varies depending on the vegetable. Winter squash, eggplant, and similar vegetables are properly cooked when they turn soft, but most vegetables are best when cooked very briefly or until they are crisp-tender. At this stage vegetables maintain their maximum flavor, color, and nutrients.
Cellulose and pectin are the fibers that give vegetables their shape and firmness. Cooking softens these fibers. The amount of fiber varies with different vegetables, with the age of vegetables, and even within the same vegetable. A longer cooking time means softer vegetables. Alkali, such as baking soda, should not be added to vegetables because it destroys vitamins and softens vegetables to the point of mush. Acids such as lemon juice, vinegar, tomato products, and sugar make vegetable fibers firmer. If you add any of these, you will need to allow more cooking time.
Starch found in vegetables also affects texture. Dry starchy foods like dried beans, peas and lentils, rice, and macaroni products must be cooked in enough water to allow the starch granules to absorb moisture and soften. Moist starchy vegetables like potatoes and yams must simply be cooked to soften the starch granules.
The longer a vegetable is cooked, the more flavor is lost. Many flavors are lost during cooking, either by dissolving into the cooking liquid or by evaporation. You can prevent significant flavor loss by cooking vegetables as quickly as possible. Start with boiling water to reduce cooking time. Use as little water as possible to minimize leaching of vitamins and minerals. Steam vegetables when possible because less nutrients and flavor are lost during the reduced cooking time.
Strong-flavored vegetables such as onions, cabbage, brussels sprouts, cauliflower, broccoli, and turnips are much more appealing if some of their flavor is lost. Cooking strong-flavored vegetables uncovered and in larger amounts of water allows off-flavors to escape.
It is important to preserve as much of a vegetable's natural color as you can during cooking. Different pigments react differently during cooking.
Chlorophyll is the pigment present in all green vegetables such as asparagus, green beans, broccoli, peas, and spinach. Chlorophyll is destroyed by acids, such as lemon juice and vinegar, and by baking soda. Prolonged cooking or overcooking causes bright green vegetables to turn a drab olive green. Steaming is the most preferred method for cooking because steam cooks food rapidly, lessens the loss of nutrients and flavor, and does not break up delicate vegetables.
Carotenoids are the yellow and orange pigments found in carrots, corn, sweet potatoes, tomatoes, and winter squash. These pigments are very stable to acids and heat, but loss of color, nutrients, and flavor occurs with overcooking.
Anthocyanins are the red pigments found only in a few vegetables, such as beets and red cabbage. These red pigments react very strongly to acids and alkalis. Acids make anthocyanins brighter red, and alkalis turn them a blue or blue-green color. So a small amount of acid gives red beets and red cabbage a bright red color. This is why red cabbage is often cooked with tart apples. Because acids toughen vegetables and prolong cooking time, in recipes that call for lemon juice, tomatoes, or other acids, add only a small amount at the beginning of cooking and the remaining toward the end after the vegetables have become tender. Because anthocyanins dissolve easily in water, cook these vegetables quickly in as little water as needed.
Flavones are the white pigments found in potatoes, onions, cauliflower, and the white parts of celery, cucumbers, and zucchini. Cook these vegetables for a short time to avoid loss of nutrients, flavor, and color. Overcooking and hard water turn white vegetables a dull yellow or gray.
Vegetables cook quickly and easily in the microwave oven. Only a few tablespoons of water are needed and microwaving preserves the nutrients, color, and texture of most vegetables. Always cover vegetables in the microwave.
This method can be used for both pressurized steam cookers and range-top steamers which contain a perforated basket over a pot of boiling water. Pressurized steamers are not recommended because it is too easy to overcook the vegetables.
Potatoes, sweet potatoes, and winter squash, as well as tomatoes, can be baked successfully. Starchy vegetables are baked because the dry heat of the oven and long baking time produce a desirable texture.
Vegetable casseroles are also baked, but precook the vegetables by simmering or steaming before they are mixed with other ingredients and baked.
Boiling is the most frequent method of cooking vegetables because it is easy and economical. Actually, simmering is the proper term. The vegetables should be simmered because the agitation and high temperature of boiling break up delicate vegetables and destroy nutrients. Simmering can be used for fresh, frozen, dried, or dehydrated vegetables.
A quicker method is to add the dried vegetables to boiling water and boil 2 minutes. Remove from the heat and let sit for 1 hour before cooking.
The differences between sauteing and frying are in the amount of fat used and the length of cooking time. To saute is to cook quickly in a small amount of fat. Frying cooks in a larger amount of fat, usually 3 inches or more, for a longer time at a lower heat. Stir-frying is similar to sauteing and can be done in a regular pan or a stationary wok. Most vegetables are fried from 325º to 350ºF after being coated with a batter or breading. Without this coating, vegetables tend to dry out. Drain excess fat from deep-fried vegetables.
Braising is a slow, moist-heat cooking method that uses a small amount of liquid. General procedures follow.
Experiment with small amounts of seasonings to find what your family will accept. Start with 1 teaspoon of mild herbs or spices, such as basil, cinnamon, cumin, lemon pepper, or oregano per six servings. With strong herbs or spices, such as allspice, cloves, ginger, nutmeg, rosemary, and tarragon, start with only ¼ teaspoon per six servings. Ground herbs are stronger than dried, and dried are stronger than fresh. If a recipe calls for ¼ teaspoon of ground herbs, use almost 1 teaspoon of dried or 2 teaspoons of fresh herbs.
Asparagus: Garlic, fresh lemon juice, onion, vinegar.
Beans: Caraway, cloves, cumin, mint, onion, green bell pepper, savory, tarragon, thyme.
Beets: Anise, caraway, fennel, ginger, savory.
Carrots: Anise, cinnamon, cloves, mint, sage, tarragon.
Corn: Allspice, chili powder, green bell pepper, pimiento, fresh tomato.
Cucumbers: Chives, dill, garlic, vinegar.
Green Beans: Dill, fresh lemon juice, marjoram, nutmeg, pimiento.
Greens: Garlic, fresh lemon juice, onion, vinegar.
Peas: Allspice, green bell pepper, mint, fresh mushrooms, onion, fresh parsley, sage, savory.
Potatoes: Chives, dill, green bell pepper, onion, pimiento, saffron, sage.
Squash: Allspice, brown sugar, cinnamon, cloves, fennel, ginger, mace, nutmeg, onion, savory.
Tomatoes: Allspice, basil, garlic, marjoram, onion, oregano, sage, savory, tarragon, thyme.
Vegetables in general: Basil, cayenne, chervil, dill, marjoram, mint, fresh mushrooms, nutmeg, oregano, parsley, freshly ground pepper, poppy seeds, rosemary, sage, sesame seeds, tarragon, thyme, turmeric, watercress.