There is a certain degree of heat which, if maintained for a sufficient
period of time, will destroy disease germs and certain other harmful
germs which tend to spoil milk, while at the same time it is not high
enough to cause the delicate flavour of raw milk to disappear. Bringing
milk to this exact condition is called “pasteurizing” it. Into feeding
bottles put the amount of milk that is to be used at one time. Plug them
with sterilized (baked) cotton. Stand them on a rack in a cooker-pail,
surrounded, to the depth of the milk, with warm water. Gradually raise
the temperature till the milk in the bottles registers 150 degrees
Fahrenheit. Cover the pail, and set it in a cooker for from twenty
minutes to half an hour or more. Remove the bottles, cool quickly and
keep the milk in a cold place, but not freezing, till needed. Do not
remove the milk from the bottles if it is used for feeding infants. If
used for adults do not remove it until it is to be used. Pasteurized
milk will keep for a long time without souring, but is dangerous unless
continuously kept very cold. Milk to be kept hot in a cooker for use in
the night, should be put in while scalding hot, not merely pasteurized,
since “any device for keeping milk [merely] warm should never be
used.”[3]
[3] “Bacteria in Milk,” by L. A. Rogers. Yearbook of the Department of
Agriculture, 1907, p. 194.