OYSTERS AND THEIR PREPARATION
82. 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. Fig. 25 shows a group of oysters and clams, the three on the left being oysters and the three on the right, clams. 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.
83. COMPOSITION OF OYSTERS.--Oysters occupy a prominent place among animal foods, because they are comparatively high in protein. In addition, they contain a substance that most flesh foods lack in any quantity, namely, carbohydrate in the form of glycogen, and for this reason are said to resemble milk closely in composition. A comparison of the following figures will show how these foods resemble each other:
| WATER | PROTEIN | FAT | CARBOHYDRATE | MINERAL SALTS | |
| Milk | 87.0 | 3.3 | 4.0 | 5.0 | 0.7 |
| Oysters | 86.9 | 6.2 | 1.2 | 3.7 | 2.0 |
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.
84. 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.
85. HEALTHFULNESS OF OYSTERS.--Much illness has been attributed to oysters, and without doubt they have been the cause of some typhoid and some ptomaine poisoning. A knowledge of the reason for these diseases has done much to eliminate them. It is now definitely known that much of the typhoid caused from eating oysters was due to the conditions under which they were grown. In their growth, oysters fasten themselves to stationary things, such as rocks or piles driven into the ground underneath the water, and they obtain their food by simply opening the shell and making use of minute particles of plant and animal life that they are able to extract from the water. When the water was not clean or when sewage was turned into it, typhoid germs were transmitted to persons who took oysters as food. At present, there is scarcely any danger from such causes, for more care is now given to the conditions under which oysters grow. Ptomaine poisoning from oysters was caused by eating them when they had been improperly cared for in storage or had been taken from the shells after they were dead. Unless persons handling oysters know how to take care of them, this danger is still likely to exist.
86. 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.