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The preservation of eggs is, therefore, materially assisted by coating the egg artificially with a varnish or film of some kind which renders the egg impervious to air and water. One of the cheapest, simplest, and best of these coatings, as has already been noted, is soluble glass. This is produced by dissolving the chemical substance known as silicate of soda in water, and dipping the egg into the solution, removing and allowing to dry. The silicate of soda which is thus left in a thin film over the surface of the egg penetrates and stops the pores and renders the egg shell practically impervious both to air and water. This material has the property of becoming totally insoluble in water when it has once been dried so that even if the egg is afterwards subjected to rain or water in any form the film is not removed. Many other methods of coating eggs have been employed and are dependent upon the same principle but are perhaps not so effectual and simple as the inexpensive method above described.
Cold Storage.-Eggs either with or without the coating of the surface, usually without, may be kept for a considerable length of time without deterioration in cold storage. In this case it is advisable to reduce the temperature to the lowest possible point to retain the semi-fresh condition of the contents. Water freezes at 32 degrees, but for the reasons above mentioned the temperature at which the egg is stored may be reduced notably below 32 degrees without danger of solidifying. The eggs kept in cold storage gradually acquire a taste and aroma which are quite different from the fresh article and the period of preservation should never be prolonged, probably a month or six weeks is the extreme limit for keeping eggs which can still be regarded as having the qualities of the fresh article. In practice, eggs are kept often a very much longer time since the principal object of cold storage is to lay in a supply in the spring and summer when they are abundant and keep them over until the next winter. The average age of cold storage eggs is probably more than six months. At this time the eggs have acquired a distinctly unpleasant odor and flavor which enables even one who is not an expert to distinguish between them and the fresh article. Such eggs should not be allowed on the market except under their proper designation so that the purchaser may know the character of the product he is getting. There is a determined opposition on the part of those dealing in cold storage eggs against such marking, an opposition which can only be explained by the fact that the amount of deterioration is fully as great as specified. If cold storage eggs have not been kept long enough to develop any of the objectionable conditions mentioned above and are inferior only in respect of taste and aroma there seems to be no just reason why they should be forbidden sale. They usually bring a lower price than fresh eggs produced at the time of sale and thus are brought more readily within the means of those who are less able to pay the higher prices. Cold storage eggs are extensively used for baking purposes and in this condition escape the detection of the consumer. This appears, however, to be no just reason for their use without notice.
Broken Eggs. An extensive industry has been practiced for many years in the product known as broken eggs. In the preparation of broken eggs at times of great abundance, the eggs are collected and broken and then mixed together in containers of various sizes, often as large as barrels, and preserved by the admixture of borax. From two to four pounds of borax are usually employed per 100 pounds of broken eggs. In this condition the eggs are kept from the time of great abundance until the time of higher prices, namely, from six to eight months, and then sent into commerce. The use of broken eggs of this kind for edible purposes is totally indefensible. While borax prevents the development of bacteria it does not entirely inhibit enzymic action and hence that subtle change of nitrogenous matter which produces poisonous bodies may go on in the presence of borax while apparently the egg itself remains undecomposed. Broken eggs were formerly sent to this country in large quantities from China and other Asiatic countries but since the passage of food inspection laws as applied to foreign commerce the importation of this class of food products has been prohibited, on the ground that they are unfit for human consumption. Other preserving agents have been used in place of borax for these products, but all are open to similar objections. Broken eggs are used chiefly by bakers in large cities.
BROKEN AND DRIED EGGS.
Dried Eggs.-The rapid drying of fresh eggs is perhaps an unobjectionable method of preservation. The drying may take place by spreading the eggs in a thin film on a dry surface, which is the usual method, or by forcing the egg product through small orifices under a high pressure into a drying chamber so adjusted as to temperature and size as to secure the desiccation of the minute particles of egg spray before they fall to the bottom. This method is perhaps the best which has yet been developed in the desiccation of such products. The egg powder thus formed is almost devoid of moisture and when properly collected and stored out of contact with the air, may be kept for a time without deterioration. Dry egg products such as have been described made from fresh eggs, may be considered unobjectionable for a reasonable length of time. Unfortunately dried products are sometimes made from decayed eggs. During the past year a factory making a product of this kind was discovered by the food inspector of one of our large cities.
Egg Substitutes.-Many products have been put upon the market of a yellow color and containing protein under the guise of eggs. There is a number of socalled egg powders offered for making cakes, etc., which contain no egg at all. They are composed of other forms of protein matter, generally casein from milk, and colored to resemble the egg in tint. Starchy substances are also colored and sold as egg powder. These substances may be regarded as adulterations when sold under the name or in the guise of an egg product. There are no other adulterations of eggs of any consequence practiced except the simulation of egg material by such products as those just mentioned.
Poisonous Principles in Eggs.-While fresh eggs for most people form a food product entirely devoid of danger, nutritious and easily digestible, eggs may easily become injurious and even poisonous. According to experiments made by Bouchard (Scientific American, August 11, 1896, page 95), even fresh eggs, unless the sanitary conditions in which the fowls live are well cared for, may become very poisonous. The fowl producing eggs, as a rule, is not a cleanly animal, and this is especially true of the duck. Thus injurious organic material rich in microbes may contaminate the egg and the microbes may penetrate the shell thus rendering the egg unsuitable for consumption. Eggs contaminated in this way have given evidence of toxic phenonema even in a fresh state. Experiments have shown too that the food material of eggs if directly injected into the blood of an animal produces toxic effects whereas if injected into the stomach no unfavorable effects are produced. Egg albumin, that is, the albumin of the white of the egg, when fed in considerable quantities to animals partially escapes digestion and thus becomes a source of irritation and even of poisoning. There are many people who are remarkably sensitive to the influence of eggs and those who possess this idiosyncrasy are injured even by eggs which are perfectly harmless to other people. A large number of species of injurious microbes which infect eggs have been identified. These even are found in fresh eggs in the unsanitary conditions above mentioned. Eggs kept for a long while in cold storage or decayed in any way are extremely injurious. Fortunately decayed eggs are self protecting since they can only be eaten by accident. If, however, decayed eggs be eaten in diluted form by mixing with other foods they may be eaten without their characteristic odor or taste being known and thus great injury arises. It is advised in all cases where eggs are to be kept for some time even in cold storage to varnish them with some substance impenetrable to air. For this purpose, as has already been mentioned, soluble glass, which is chemically a silicate of soda, has been found extremely effective. Any of the varnishes which make the shell of an egg air tight tends to restrain the activities of bacterial life since the bacteria cannot live without air. The officials who inspect food should direct special care to the storing of eggs in order that no damage may result from keeping them too long in cold storage or otherwise. It must not be understood that poisoning by eggs is of common occurrence. In fact it is very rare. The fact that the egg itself, which is such a common article of diet, may be unsanitary and improperly kept is a matter of great concern to the consumer.
Parasites in Eggs.-The egg also when produced in unsanitary conditions may become infected with parasites. Many of these are apparently harmless, but some are injurious and even dangerous. The mere fact that parasites may exist in eggs is of itself a sufficient reason for the consumer to insist that the eggs he eats, like the milk he drinks, shall be free from all infections due solely to carelessness in production.
Fish furnish a very important and useful part of the animal food of Both the fish growing in fresh water and in salt water are generally edible. Usually the smaller-sized fish are considered more palatable, but this is not universally the case. The large-sized fish are apt to be coarse, and have a less desirable flavor than those of smaller size. The size of the fish usually depends upon the magnitude of the body of water in which the species grow, the largest being in the lakes and oceans, the medium-size in rivers, and the smallest in brooks. Fish are known chiefly by their common names, and these names are different for the same species of fish in different parts of the country. For instance, the term trout covers a multitude of species, and, likewise, under the term sardine a large number of different species or varieties of fish are considered. There is also a large number of varieties known as salmon, perch, bass, etc.
In the following table are given the common and the scientific names of the principal food fishes used in the United States (see Report of U. S. Commission of Fish and Fisheries, 1888, pages 679-868):
Acipenser sturio oxyrhynchus, Sturgeon. Catostomida:
Moxostoma velatum, Small-mouthed red-horse.
Clupea harengus, Herring.
Osmerus mordax, Smelt.
Coregonus clupeiformis, Whitefish.
subsp. sebago, Land-locked salmon.