Page:Popular Science Monthly Volume 81.djvu/162

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156
THE POPULAR SCIENCE MONTHLY

can penetrate the shell, especially if the shell is moist. These bacteria find excellent food in eggs and will multiply at an enormous rate unless the eggs are kept cold. The producer usually brings the eggs once a week to the country store, where they remain for another week or two before being delivered to a factory for desiccation. When we consider that one bacterium may have a progeny of 17 millions in 24 hours under favorable food and temperature conditions, it is not surprising to find that eggs used for desiccation contain millions of microorganisms. Bad eggs are usually recognized by holding them up to a bright light in a dark room, a process known as "candling." This will reveal dark spots resulting from bacterial multiplication, or colonies of molds, or embryonic development of the chick. But we must remember that millions of bacteria take up a smaller space than the head of a pin, so that the process of candling will show their presence only after enormous multiplication has taken place. On the other hand, if fresh eggs are desiccated within a few hours or a day after laying and have been kept cold during this interval, the final product will contain about the same number of bacteria as the original eggs. It must not be assumed, however, that the presence of many millions of bacteria is necessarily injurious to health. Of all species of bacteria known to science an exceedingly small number is injurious, and these are rarely found in eggs.

 

Conservation by Cold Storage

The present methods of cold storage are the natural result of evolution from the practise of using the cellars of farmers and produce dealers. Surplus food material is stored in warehouses, where it will keep in good condition for various periods of time, these periods depending largely upon the degree of temperature maintained. Such storage makes possible an artificial season, which may be long enough to bridge the gap between one producing season and the next. The importance of this can not be overestimated and has found expression in the fact that the Canadian government is subsidizing cold-storage plants.

The degree of temperature to which foods are exposed in cold storage varies according to the nature of the food. Fruits, vegetables and and shell eggs are permanently injured by freezing and are therefore kept just above the freezing point. If eggs are broken, the yolks and whites mixed and then frozen, they can be preserved for a long time. What has been said about desiccated eggs applies with equal force to frozen and cold storage eggs. If they are in good condition when placed in cold storage or when broken for freezing they will keep for a long time. Usually considerable deterioration takes place before they reach the packer. Especially is this true of summer eggs. April and May eggs, if placed in cold storage in good condition, are of better quality