Page:Popular Science Monthly Volume 55.djvu/654

634 the milk, although it will keep some time, is not indefinitely preserved. The common method used is heating with superheated steam. The milk is placed in bottles of special device, holding about a pint or a quart, and are placed, hundreds at a time, in a large chamber which can be hermetically sealed and then filled with steam under pressure. Here the temperature rises to 102° to 106° G. (216° to 220° F.), and is retained here for some little time. This high heat is supposed to kill all the living bacteria that may be in the milk, even the resisting spores being commonly destroyed. While the milk is still in this apparatus, and before the chamber is opened, the bottles are sealed by a mechanical contrivance and then allowed to cool. After this they are taken out of the sterilizer, and are ready for distribution. The milk thus treated is sometimes pure white, although frequently it has acquired a brownish color, which is not enticing to one accustomed to ordinary milk. Moreover, it has a taste of cooked milk, which is to some people very unpleasant. But when the method is successful the milk contains no living bacteria, and may now be kept indefinitely without further change. It may be shipped to all parts of the world, and whenever opened it will be found still sweet. The process is evidently equivalent to the canning of fruit or meat, only more difficult because the milk commonly contains many resisting spores.

Such sterilized milk can be bought almost anywhere in Europe, and there is undoubtedly a growing demand for it. Where this or other sterilized milk is used it is claimed that very favorable results follow. Careful statistics have been collected as to the number of deaths among infants from diarrhœal diseases, and it is found that in some cities the deaths from infants fed upon raw milk are nearly three times as great as among those fed upon sterilized milk. Of course, no typhoid epidemics can ever be traced to such milk, and in general its use seems to meet with decided favor.

There are, however, some serious objections to this method of treating milk, which have been and probably will continue to be sufficient to prevent its wide extension. The first is that such milk appears to be slightly less digestible than raw milk. Over this matter, however, there has been and still is a great diversity of opinion, and many claim that there is really no difference in the digestibility. It is a matter of comparatively little importance, however, at least for adults and healthy children, for the sterilized milk can be digested, and the slight difference in ease of digestion probably has little significance unless it be for weakly individuals. Secondly, the taste of the sterilized milk is that of boiled milk, and this is rather unpleasant to most people. Probably a majority of our people, if called upon to drink sterilized milk or none at all,