Cookery And Food Preparation
( Originally Published 1921 )
COOKING is the application of heat to foods, to render them more digestible and better fitted to nourish the system. There are comparatively few foods that are at their best when taken in their raw state. They neither taste so good nor are so easily digested as when subjected to some kind of cooking.
The nutritive value of many foods depends upon how they are cooked. Many articles that, owing to their chemical condition or other cause, are unfit. for nourishment when raw, are very nutritious when cooked. The direct application of heat changes the taste, odor, and digestibility of nearly all foods, and changes the food elements (with the exception of fats) in much the same way as do the digestive juices. Many inexpensive articles and "left overs," if carefully prepared and attractively served, are just as appetizing as the more expensive foods, and are usually quite as nutritious.
OBJECTS SOUGHT IN COOKING
There are three chief objects sought in cooking. The first is to change the mechanical condition of food so as to make it more digestible. The second is to develop its flavors, thus conserving its nourishment and making it more palatable and inviting. The third is to kill, by heat, any disease germs, parasites, or other dangerous organisms it may contain.
Boiled starch is soluble, and is acted upon by the saliva in mastication, which changes it to dextrin. This process is for-warded by the organs of digestion to maltose, dextrose, blood, etc. Raw starch is insoluble, and is not acted upon by the saliva, and only in small quantities by the intestinal fluids. So in order for man to appropriate it, the woody envelope that incloses the starch granule must be broken, by being subjected to dry or moist heat, as illustrated in the following cuts.
When put into boiling water, the cellulose surrounding the starch grains breaks, setting free the granulose, which takes up the water, forming a thick, transparent mass. Water has little effect on starch granules until this cellulose covering has been thus broken. The softening and rupture of the cellulose frame-work of vegetable cells, allowing the starch grains to become jelly-like, is one of the chief aims sought in the cooking of vegetable foods.
Ripe fruits, on the other hand, have been virtually cooked on the tree, and are best when eaten thus, without being subjected to artificial heat. The carbohydrate of fruit in its unripe state is in the form of raw starch. As the fruit ripens, this starch is changed to sugar, and is practically ready to be absorbed by the digestive organs. The same is true of tomato. Thus no cooking is required for ripe fruits, except to preserve them for future use, by canning, etc. It is with starch that cooking has most to do, as starch in its raw state cannot be utilized by the body, and it is the most abundant of all food elements.
In the second object, development of food flavors, the preservation of the mineral salts and vitamines is of paramount importance. The manner in which fresh vegetables are often cooked deprives them of a large part of these essential constituents, and thus robs them of their characteristic flavors. This has special reference to the boiling of vegetables in water, throwing the water away, and then serving up the more or less insipid residue.
When tea was first introduced into England, a certain peddler (so the story is told) called at a farmer's house and sold half a pound of tea to the wife. About a month later he called to ask her how she liked it. She told him they did not like it at all. Then he asked her how she had prepared it. She said she had boiled it like cabbage and had thrown the water away, but that they "could not eat the stuff!" All very good, perhaps, in the case of tea; but unfortunately, many people treat vegetables in the same way. The important inorganic salts and mineral sub-stances so abundant in fresh vegetables are more or less drawn out into the water in which the vegetables are cooked. When this is thrown away, a most valuable part of the food is wasted. The same treatment is often given to cereals and legumes; after being boiled in a large quantity of water, they are drained, and the water is allowed to run down the drain pipe of the sink.
For this same reason, the potato is far more nutritious if baked or boiled in the skins. The carrot, when scraped, sliced thin, and allowed to simmer until the liquid is mostly evaporated, will have a delicate yellowish color and pleasant flavor, with its salts and minerals conserved.
Most of the succulent vegetables are best when steamed, or cooked in only sufficient water to make them tender; and the remaining liquid should be regarded as the most essential part of the food. When vegetables are thus cooked conservatively — that is, in such a way as to retain their juices — they possess a far richer flavor than when deprived of their juices by swimming in a large quantity of water. To this rule, there are a few exceptions. Old cabbage, for instance, is likely to have a strong flavor and a dark color if cooked by this method; but if the leaves are pulled apart and then dropped into deep boiling water, they will retain their delicate green color and will have a mild flavor in contrast to the dark color and strong flavor that result when it is cooked in compact form or in large pieces. When cabbage is very tender and crisp, if shredded fine, it may be cooked in a covered vessel, with the addition of a little vegetable butter, and no water, the vessel being covered, and the cabbage stirred often. The moisture in the vegetable is sufficient.
During the cooking of green vegetables, such as new peas, string beans, etc., the cover should be drawn a little to one side of the stewpan or kettle, so as to allow the escape of the steam, which is laden with volatile bodies that will, if retained, impart to the vegetable a strong flavor and a dark color.
Mustard greens, beet and turnip tops, spinach, etc., after being washed in several waters to remove grit, should be put to cook in deep boiling water with the cover off. The reason why greens, especially those well grown, require more water in the cooking than ordinary succulent vegetables, is that in growing for some time exposed to the sun, they develop a bitter flavor, and this is largely extracted by this manner of cooking. When spinach is very tender, it may be cooked with no additional water beyond that remaining on the leaves after washing. During the cooking, it should be turned over occasionally with a fork or a spoon, the saucepan being covered, to inclose the steam. It will require but a few minutes' cooking. Serve without chopping.
Fresh vegetables should be thoroughly cooked, but the cooking should stop when the vegetable is yet firm. Overcooking toughens the texture of vegetable foods, destroys the coloring matters, and injures the mineral bodies that contribute to their flavor and nutriment. Vegetables should be allowed to boil slowly during the cooking process, as rapid boiling tends to chip off the surface of the food, making it less palatable, and causing a loss in nutriment. Rapid boiling hardens some foods; for instance, green corn, which should be put into boiling water, brought to the boiling point, and then drawn to the side of the stove for twenty minutes.
A most valuable form of vegetable food is raw green stuff, containing the organic salts unchanged by heating. This includes such foods as lettuce, water cress, celery, cabbage, radishes, cu-cumbers, and ground, chopped, or diced raw vegetable salads. In these, the cellulose is best when eaten crisp; and their mineral salts, largely lost in cooking, are preserved.
The third object of cooking is the destruction of disease germs or other dangerous organisms that may be present. Vegetables and some fruits may become contaminated with the eggs of parasites from fertilizers applied to them. Hence raw fruits and vegetables should always be thoroughly washed before they are served, if there is any doubt as to their cleanliness.
The bacteria of typhoid fever sometimes find their way into drinking water, and those of typhoid and diphtheria into milk, bringing disease and death to many. Thus food and drink may become dangerous purveyors of disease. When food and drink are sufficiently heated in cooking, all organisms are killed.