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.
