The class of foods known as vegetables vary very greatly both in composition and as to structure. Every part of a plant including root, tuber, bulb, stem, leaf, seed and fruit is represented in this group.
From the group is excluded the seeds of the grass family, . or cereals, and the fruit of trees.
Vegetables are characterized by a low nutritive value, though a few are comparatively high. With the exception of the legumes, which are sometimes given a special classification on account of their very high nutritive value and high protein content, potatoes are the most nutritive.
Vegetables are also characterized by a large amount of cellulose and by their richness in alkaline mineral salts.
The cellulose is desirable because it gives the necessary bulk. Mineral matter is necessary for maintaining the alkalinity of the blood and for the repair of the bony structures.
It is important that vegetables should be prepared and cooked in such a way as to conserve all available food material and mineral salts.
The portion of the vegetable next to the skin contains the greater quantity of mineral matter, protein and fat, hence all thin skinned vegetables such as new potatoes, carrots and vegetable oysters should be scraped. Other vegetables should be pared as thinly as possible.
When the liquid in which vegetables are cooked is drained off, it carries with it much that is valuable. As far as possible this should be saved and used as the foundation for soups or sauces, or better still, cook the vegetable in a steamer, thus conserving the entire food value.
Vegetables should be cooked only until tender. Many vegetables develop a strong and unpleasant flavor and are rendered less easily digested by over cooking. This is especially true of cabbage, cauliflower, etc. When overcooked they also take on a reddish hue.
All vegetables should go over the fire in boiling water.
Fresh succulent vegetables should always be put to cook in salted water. Old vegetables that have become somewhat tough should have the salt added a few minutes before the cooking is finished.
Peas, beans and lentils should always be cooked in un-salted water, as the salt combines with the legumin, a form of protein, and forms an insoluble compound, thus making them very difficult to cook. Soft water should be used if possible.
Old vegetables may be made much more tender by immersing an hour or more in cold water.
Asparagus, lettuce and other succulent vegetables may be refreshed by standing in cold water.