EXPERIMENT 63. PROTEIN IN OYSTER LIQUOR.—Pour a small quantity of oyster liquor into a test tube and boil it. What change takes place? From your previous experience with eggs, what foodstuff would you infer that oysters contain? What inference can you draw from this as to the temperature at which oysters should be cooked?

OYSTERS.—An oyster is an animal covered with shell. The shell, which consists of mineral matter, protects the animal.

[Illustration: FIGURE 74—COMPOSITION OF FISH, FISH PRODUCTS AND OYSTERS
(Revised edition)]

The oyster has no head, arms, or legs, but it has a mouth, liver, gills, and one strong muscle. The mouth is near the hinge-end of the shell; by means of the hinge, the shell is opened and water and food taken in; by means of the muscle, the shell is closed. (Find the muscle in an oyster; then the dark spot,—this is the liver; also find the fluted portions that partly surround the liver,—these are the gills.)

Oysters are in season from September until May. They are sometimes eaten during the summer months, but are not so palatable and are more apt to be contaminated by the bacteria of warm water. The bluish green color of some oysters is due to the oyster's feeding upon vegetable materials. This does not harm the flavor of the oyster.

Oysters are sometimes placed in fresh water streams or in water which is less salt than that in which they have grown to "fatten them." The animals take in the fresh water, become plump, and increase in weight. If the water is sewage-polluted, the oysters become contaminated with dangerous bacteria. Methods of cooking usually applied to oysters, such as stewing and boiling, may not destroy all bacteria. Hence, the danger in eating oysters taken from polluted water.

When oysters are prepared for market, they are sorted according to size. Blue points, or small oysters originally grown in Blue Point, are prized for serving raw in the half shell. This name, however, no longer indicates the place from which the oysters come, but is applied to small oysters in the shell. Large oysters selected for frying may be purchased. Oysters are found at markets either in the shell or with the shell removed.

Since oysters spoil readily, they must be kept cold during transportation. They are now shipped in containers surrounded by ice. Formerly ice was placed in contact with the oysters.

Note the percentage composition of oysters (see Figure 74). With such a large quantity of water, the oyster has little food value. Oysters are prized for their flavor, but make an expensive food. Cooking makes oysters somewhat tough, but it sterilizes them and makes them safer to use. It is considered that oysters properly cooked are easily digested. They should be eaten when very fresh. They spoil quickly and develop poisonous products.

CLEANING OYSTERS.—Drain off the liquor. If the liquor is to be used, strain it through a fine strainer. Place the oysters in a strainer or colander, and wash them. Do not allow oysters to stand in water after washing. Run each oyster through the fingers to remove pieces of shell that may be clinging to it.

OYSTER STEW

1 cupful milk 1 pint oysters 1 tablespoonful butter Salt and pepper

Heat the milk in a double boiler; add the seasonings and butter. Clean the oysters; cook them in a saucepan until they become plump and the edges curl. Add the hot milk and serve at once.

The milk may be thickened with 1 tablespoonful of flour (see recipe for Thin White Sauce).

Serve crackers or bread with Oyster Stew.

SCALLOPED OYSTERS

1 pint oysters 1/2 teaspoonful salt 3 cupfuls soft bread crumbs 3 tablespoonfuls butter or substitute 1/4 cupful oyster juice or milk Cayenne

Wash the oysters, strain the juice, and butter the crumbs. Add the seasoning to the oysters. Place one fourth of the buttered crumbs in the bottom of a buttered baking-dish. Add one half of the oysters, another fourth of the crumbs, then the remainder of the oysters, the liquid, and finally the remaining half of the buttered crumbs. Bake in a moderate oven from 30 to 40 minutes.

If baked in individual baking-dishes, only 15 minutes will be required for baking.

QUESTIONS

Count and record the number of oysters in one pint.

From Figures 64 and 74, tabulate the percentage composition of oysters and milk.

Find the weight of one cupful of oysters and of one cupful of milk. How do they compare as to the amount of water, protein, and fat contained in one pint of each?

What is the difference in cost of one pint of each?

What is the purpose of straining the oyster liquor?

Why should not oysters stand in water after washing (see Experiment 38)?

Explain why oysters should be cooked only a short time. What is the effect of long cooking upon oysters?

In Scalloped Oysters, why is the liquid added before the last layer of crumbs?

How many persons do each of these oyster recipes serve?

What dietetic reason can be given for combining oysters and bread?

From U.S. Department of Agriculture Bulletin No. 28, tabulate the percentage composition of the following fish: Fresh and salt cod, fresh and smoked herring, fresh and salt mackerel, fresh and canned salmon, fresh perch, and fresh white fish. Which contains the most fat? How can fish be classified with regard to fat content (see Classes of Fish)? Which fish contains the most protein?

How do fish, shellfish, and beef compare in protein content? Which is the cheapest source of protein (see Figures 68 and 74)?