OYSTERS, CLAMS, and SCALLOPS are salt-water fish that belong to the family of mollusks, or soft-bodied animals. They are entirely encased in hard shells, which, though of the same general shape, differ somewhat from each other in appearance.
Oysters are larger than clams and have a rough, uneven shell, whereas clams have a smooth, roundish shell. The three varieties of mollusks are closely related in their composition and in their use as food, but as oysters are probably used more commonly than the others they are considered first.
Oysters, as will be observed, contain only a small quantity of fat, and for this reason their total food value is somewhat lower than that of milk. A pint of milk has a value of 325 calories, while the same quantity of oysters has an approximate value of only 250 calories.
Because of the difference in the cost of these two foods, oysters costing several times as much as milk, the use of oysters is not so cheap a way of supplying food material.
DIGESTIBILITY OF OYSTERS
When merely the ability of the digestive tract to handle oysters is taken into consideration, they are said to be easily digested if they are served raw or are properly prepared.
This is due to the fact that when taken as a food they are disposed of in a comparatively short time by the stomach. In addition, their absorption from the alimentary tract is quite complete; that is, they contain little or no waste material. But, just as cooking has much to do with the digestibility of other protein foods, so it has with oysters.
For this reason, the housewife who wishes to feed her family this food in its most digestible form must thoroughly understand all phases of its cooking.
PURCHASING OYSTERS
To be able to purchase oysters intelligently, the housewife should be familiar with the names of the various kinds. These names are dependent on the locality from which the oysters come, and include Blue Points, Cape Cods, Cotuits, Lynn Havens, and numerous other varieties.
It should be remembered that the varieties raised in different localities are quite distinctive, differing to some extent in both size and appearance. Unless the purchaser is familiar with the different varieties, almost any of the small oysters are likely to be sold to her for one of the small varieties and, likewise, any of the large oysters for one of the large varieties.
While this is of small consequence, provided the quality is satisfactory and the price is right, it is well for every housewife to familiarize herself with the names of the various kinds, so that she may know just what variety she is purchasing
When oysters are bought in the shell, they should be alive, a fact that can be determined by the tightly closed shell, as has already been stated. If the shells are not closed or can be easily pried apart, it may be known that the oysters are not good and that they should be rejected.
When it is possible to procure them, oysters that have been removed from the shells immediately after being taken from the beds are preferable to those which have not been removed from the shells before shipping. When purchased out of the shells, oysters should be grayish in color, should have no disagreeable odor, and should contain no excess water or liquid.
After being purchased, oysters should be kept on ice unless they can be cooked at once. The season for oysters is from September to April, inclusive. While in some localities they can be purchased at other times during the year, they are not likely to be so good. In fact, it is not safe to use oysters during the warm months.
IMPORTANT POINTS IN COOKING OYSTERS
The protein of oysters, like that found in other foods, is coagulated by heat. Long heat, provided it is sufficiently intense, makes oysters tough, and in this condition they are neither agreeable to eat nor readily digested. When they are to be cooked at a high temperature, therefore, the cooking should be done quickly.
If they are to be cooked at a temperature below the boiling point, they may be subjected to heat for a longer time without becoming so tough as when a high temperature is used. Cooking quickly at a high temperature, however, is preferable in most cases to long, slow cooking.
For example, in the preparation of oyster stew, long cooking produces no better flavor than short cooking at a high temperature and renders oysters far less digestible.
OPENING OYSTERS
Unless oysters are bought already opened, it becomes necessary to open them in the home before they can be served raw or cooked. To open oysters is not difficult, and with a little experience the work can be done with ease. It will be well to note that the two shells of an oyster, which are called valves, are held together by a single muscle, known as the adductor muscle, that lies near the center, and that this muscle must be cut before the shell will open readily.
Before attempting to open oysters, however, they should be scrubbed with clean water, so as to remove any sand that may be on the shells. When the oysters are cleaned, insert the point of a knife into the hinged, or pointed, end and push the blade between the valves until they appear to separate, when it will be known that the muscle has been cut.
Then, lay the valves open and loosen the oyster from the shell by slipping the knife under it. If the oysters that are being opened are to be cooked before serving, simply drop them with their liquid into a suitable vessel and discard the shells.
Before using the oysters, remove them from the liquid, look them over carefully to see that no small particles of shells cling to them, and wash them in clean, cold water to remove any sand that may be present.
Also, strain the liquid through a cloth, so that it will be free from sand when used in the preparation of the dish for which the oysters are to be used or for the making of soup or broth.
Oysters that are to be eaten raw are frequently served on the half shell. Therefore, if they are to be used in this way, place each oyster, as it is loosened in the process of opening, into the deeper shell, and discard the other one.
Very often good-looking oyster shells are saved in order that they may be used from time to time in serving raw oysters that are bought already opened.