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UNITED STATES DEPARTMENT OF AGRICULTURE 
s\jp"&jl. 
BULLETIN No. 342 
Rev.ed. 
follows 
Washington, D. C. 
Issued January 8, 1916; revised September, 1S26 
THE PRESENT STATUS OF THE PASTEURIZATION 
OF MILK 
By S. Henry Ayers, 1 
Bacteriologist, Bureau of Dairy Industry 
CONTENTS 
Meaning of the term Pasteurization- 
Value of Pasteurization 
Electrical and ultra-violet-ray treat- 
ment of milk 
Extent of Pasteurization in the 
United States 
Methods of Pasteurization 
Advantages of low-temperature Pas- 
teurization 
Temperatures and methods most 
suitable for Pasteurization 
Supervision of th<> process 
Page 
1 
Page 
Handling milk after Pasteurization- 10 
Cost of Pasteurizing milk n 
Bacteria which survive Pasteuriza- 
tion ii 
The colon test for efficiency of Pas- 
teurization 13 
Past and present theories of Pasteur- 
ization 14 
Pasteurization and vitamins 15 
Pasteurized milk for infants 15 
The necessity for Pasteurization 16 
References to literature 17 
MEANING OF THE TEEM PAS- 
TEURIZATION 
The term " Pasteurization " origi- 
nated from the experiments of Louis 
Pasteur, in France. From 1860 to 
1864, in experiments on the " dis- 
eases " of wine, he found that heat- 
ing for a few moments at tempera- 
tures of from 122° to 140° F. was 
sufficient to prevent abnormal fermen- 
tations and souring in wine. A little 
later he found that by a similar heat- 
ing beer could be preserved from sour- 
ing. The application of the process 
gave rise to the term " Pasteuriza- 
tion." As applied under commercial 
conditions, Pasteurization is the proc- 
ess of heating for a short or a " long 
period, as the different processes de- 
1 Mr. Ayers resigned from the department 
in 1923. The section pertaining to extent 
of Pasteurization in the United States has 
been revised by C. S. Leete. of Market Milk 
Investigations! 
6552°— 26 1 
niand, at temperatures usually be- 
tween 140° and 185° F. As applied 
to milk for direct consumption, Pas- 
teurization should mean a process of 
heating to 145° F. and holding at that 
temperature for 30 minutes. The proc- 
ess is followed by rapid cooling. 
It is believed that the term " Pas- 
teurization " should be applied only to 
the process of heating at 145° F. for 
a period of 30 minutes. 
YALUE OF PASTEURIZATION 
From a sanitary standpoint, the 
value of Pasteurization is of greatest 
importance when market milk is un- 
der consideration. The Pasteuriza- 
tion of milk, when the process is 
properly performed, affords protection 
from pathogenic organisms. Such 
disease-producing bacteria as Bacillus 
tuberculosis, B. diphtheriw, B. typhi, 
and other organisms of the typhoid- 
