THE STERILIZATION OF MILK.
The domestic sterilization of milk by boiling, says the Public Health Journal, is now much practiced in private houses. It is apt to be ineffective on account of the difference of temperature of the fluid in the upper and the lower portion of the vessel in which it is boiled. In the usual method of sterilizing milk by cooking it in a receptacle placed in boiling water, a “bain-marie,” in fact, it is found that the temperature of the milk in the upper portion of the vessel rises much more rapidly than that at the bottom. In experiments recorded in the British Medical Journal in one instance it was found that after the milk had been on the fire for fourteen minutes the temperature at the top was 160° Fahr. while at the bottom it was only 133° Fahr. In another experiment with a stronger flame these differences were less marked. These tests prove that the mere scalding of milk by bringing the outside water to the boiling point is quite inadequate to sterilize tuberculous milk. To insure effective results, it is necessary that the heating process shall be continued until a uniform temperature throughout the entire body of milk has arisen from 190° Fahr. to 198° Fahr. This will require an exposure to a brisk fire of at least twenty-five minutes. In order to be perfectly safe, however, it is recommended that every part of milk treated in this fashion be heated for half an hour, that is, for about twenty minutes after the water in the outer pan has begun to boil.