87. 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.
88. 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.
89. 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, proceed to open them in the manner shown in Figs. 26 and 27. First, as in Fig. 26, 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, as in Fig. 27, 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, as Fig. 27 shows, 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.
90. RAW OYSTERS.--When an appetizer is desired in a meal that is to consist of several courses, raw oysters are often used for the first course. Oysters that are to be eaten raw may be served in the shells or removed from them. They are bland in flavor, however, and require some sharp, highly seasoned sauce in order to give them sufficient snap. The sauces commonly used for this purpose include cocktail sauce, chilli sauce, catsup, horseradish, and tobasco sauce. Sometimes, though, lemon juice or vinegar and pepper and salt are preferred to sauce. As a rule, crisp crackers, small squares of toast, or wafers and butter accompany raw oysters in any form, and sometimes celery and radishes are served, too.
91. When a cocktail sauce is served with raw oysters, they are generally referred to as OYSTER COCKTAILS. Two methods of serving these are in practice. In one, as shown in Fig. 28, the cocktail sauce is put into a small glass placed in the center of a soup plate filled with cracked ice, and the oysters, usually six in half shells, are arranged around the glass, on the ice. In the other, as shown in Fig. 29, the desired number of oysters that have been removed from the shells are dropped into a stemmed glass containing the cocktail sauce, and the glass is placed in a bowl of cracked ice. An oyster fork, which is a small, three-pronged fork, is always served with raw oysters, and usually a piece of lemon is supplied in addition to the cocktail sauce.