. Bacteriology and the public health. Bacteriology; Public health. CONTROL OF THE MILK SUPPLY 229 Low temperatures, it is true, do not easily destroy life, but they have a most beneficial effect upon the keeping quality of milk. It has been suggested that at the outset of the process of cooling, currents of air, inimical to bacteria, are started in the milk. If, however, the temperature be lowered sufficiently, the contained bacteria become inactive and torpid, and eventually are unable to multiply or produce their characteristic fermentations. At about 50° F. (10° C.) the activity ceases, and
. Bacteriology and the public health. Bacteriology; Public health. CONTROL OF THE MILK SUPPLY 229 Low temperatures, it is true, do not easily destroy life, but they have a most beneficial effect upon the keeping quality of milk. It has been suggested that at the outset of the process of cooling, currents of air, inimical to bacteria, are started in the milk. If, however, the temperature be lowered sufficiently, the contained bacteria become inactive and torpid, and eventually are unable to multiply or produce their characteristic fermentations. At about 50° F. (10° C.) the activity ceases, and at temperatures of 45° F. (7° C.) and 39° F. (4° C.) organisms are practically deprived of their injurious powers. If it happens that the milk is to be conveyed long distances, then even a lower temperature is desirable. The most important point with regard to the cooling of milk is that it should take place immediately. Various kinds of apparatus are. Pig. 23.~"Ulax" Filter. effective in accomplishing this. Perhaps those best known are Lawrence's cooler and Pfeiffer's cooler, the advantage of the latter being that during the process the milk is not exposed to the air. It must not be forgotten that cooling processes are not sterilising processes. _ They do not necessarily kill bacteria; they only inhibit activity, and under favourable circumstances torpid pathogenic bacteria may again acquire their injurious faculties. Hence, during the cooling of milk greater care must be taken to prevent aerial contamination than is necessary during the process of sterilising milk. No cooling whatever should be attempted in the stable; but, on the other hand, there should be no delay. Climate makes little or no difference to the practical desirability of cooling milk, yet it is obvious that less cooling will be required in the cold season. The final treatment of milk lias in practice comprised the addition of preservatives, filtration, and Please note that the
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