This section is from the book "The American Woman's Cook Book", by Ruth Berolzheimer. Also available from Amazon: The Domestic Arts Edition of the American Woman's Cook Book.
Many vegetables can be and are eaten uncooked with all their values intact. But many more need to be cooked before they can be served. Preparation by cooking should result in the least possible loss while it enhances values not otherwise available. For this reason cooking should:
1. Swell and burst the starch cell so that the center is softened and made digestible.
2. Sterilize the vegetable thoroughly.
3. Break up tough fiber so it is edible and digestible.
4. Release food proteins and minerals from their fiber cells.
5. Provide hot food.
6. Increase many flavors and some colors.
Baking is the best method to secure all these results and still preserve Vitamins and minerals. Dry baking in their skins, generally used for potatoes, sweet potatoes, squash, turnips, carrots, onions, and parsnips, is a simple method whereby the vegetable is packed in a pan or laid on the rack of a hot oven to remain until just tender when pierced with a sharp fork. Baking, however, also includes the roasting of whole vegetables with meat, gravy, or fat, especially when potatoes or sweet potatoes are scraped, thus preserving mineral values just under the skin.
Au Gratin and Scalloping are other forms of baking, especially when fresh vegetables are used. In the latter method, layers of the vegetable are alternated in a baking dish or ring mold with white sauce, cream or milk, and seasonings, and in the former method a covering of buttered bread crumbs or buttered crumbs and cheese is added. Leftover cooked vegetables may be prepared by these methods also, but the Vitamin and mineral value will be determined by the first cooking. Only baking in the jacket will insure the preservation of the Vitamins.
Broiling is the exposure to direct heat and can be used for some vegetables. The minerals will be less injured than the Vitamins, for the high heat destroys most of the latter.
Deep Fat Frying, next to baking, is another satisfactory way to retain most of the food values. The vegetable is sliced or cut into convenient form, dipped in egg and crumbs or batter, and immersed in enough very hot fat to cover well. This permits quick cooking with little loss.
In Sauteing, the shredded or broken vegetable is turned into a shallow pan or skillet in which a small amount of fat has been heated. Cooking takes longer and more fat is absorbed by the food, hence, for many persons the process is not advisable.
Boiling does the most damage to fresh vegetables, yet it is used most frequently by the largest number of homemakers. Although there are methods that reduce the losses to a minimum, the modern woman will remember that boiling is to be used least often, and always to be overbalanced by the better methods. Most of the mineral salts occurring in vegetables are easily dissolved in water and the loss of Vitamins during boiling takes place in several ways. They may be destroyed by overheating, by prolonged exposure to the air, and by dissolving out in the cooking water. When this is drained off and discarded, the principal food values gained by the intelligent buying of vegetables has been thrown away. In every case only the smallest possible amount of water should be used and it should be boiling rapidly when the vegetables are dropped in. They should be cooked only until just tender, and by this time most of the water has been evaporated. Greens such as spinach, chard, and dandelions need only the water that clings to the leaves. They go into a cold pot with the heat turned on after the vegetable is in the kettle.
To Boil Vegetables the Proper Way, four methods must be taken into account:
1. The green vegetables are best cooked in water that is slightly alkaline. If there is any doubt, add a bit of baking soda the size of a pinhead. No drinking water would be acid enough to need more. Use an uncovered kettle and cook only until tender to the fork. If overcooked, green vegetables turn brownish because of chemical changes in the coloring matter, the fine flavor is ruined, while food values are lost.
2. White fresh vegetables such as cabbage, cauliflower, and onion are strong flavored, due to their special oils. Hard water changes these oils so that the white color turns to yellow or brown. To prevent this, add 1 teaspoon of lemon juice or white vinegar. Drop the vegetable into enough rapidly boiling water to cover and cook with the kettle uncovered until just tender to the fork. Add the drained water, if any, to your soup stock.
3. The red color in vegetables is produced by acid and needs to be kept that way. Tomatoes usually have enough acid of their own to keep the color, but beets and red cabbage need a teaspoon of lemon juice or white vinegar. Cook in a small amount of water in a covered kettle.
4. Yellow vegetables are among the most valuable and stable. That rich yellow color is not only beauty but actually the foundation of Vitamin A. Not much damage can be done to it although the minerals and other Vitamins can still be destroyed if the vegetable is carelessly handled.
In general, the destruction of Vitamins is reduced when vegetables are boiled at high temperatures for the shortest possible time, in the smallest possible amount of water. Then the minerals, too, will be saved.
Steaming as a method of cooking vegetables is valuable for those that can stand a high temperature for a long period, or those that are cooked in the meat pot so that the extracted minerals and Vitamins are used in the gravy. It is particularly good for dried and starchy ones. The long, slow process gives the starch cell time to swell and gelatinize. It is most valuable at high altitudes, because the extra pressure keeps the steam at 212° F. or more, while in the open-air cooking the high altitude reduces the boiling point below 212° F.
Waterless Cooking of fresh vegetables is any process in which no water is added. The water in the vegetable itself does the cooking. A thick-walled kettle with a tight-fitting lid is the necessary equipment. Very low heat is used, and the vegetable is tender in a very short time because neither heat nor steam escapes. No minerals are lost and the loss of Vitamins is almost as low as in baking.
All cooking of vegetables reduces the Vitamin C content, although tomatoes and the baked potato manage to retain most of theirs. To insure an adequate daily supply of Vitamin C, the modern woman never loses sight of the fact that some fresh fruits and vegetables must be served every day.