222 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
There should be an accurate thermometer in the out- 
flow pipe of the pasteurizer and one in the outflow pipe 
of the holder. A reliable temperature and time-record- 
ing apparatus should be connected with both thermom- 
eters and the records should be kept on file for official 
inspection. These records should show the time of hold- 
ing as well as the temperature. The efficiency of the 
pasteurizing apparatus should also be tested frequently 
by bacteriological tests. 
The commercial pasteurization of milk should be 
permitted only under careful and competent official su- 
pervision. The inefficiency of commercial pasteurization 
without proper supervision has been frequently demon- 
strated. Two of the worst milk-borne epidemics which 
have occurred within recent years (Chicago 1911, Balti- 
more 1912) were due to infected milk which was sup- 
posed to have been pasteurized. 
Biorization.—This process consists in spraying milk 
into a chamber in which it is exposed to a temperature 
of 167° F. (75° C.) while under a pressure of 3 to 4 
pounds. The apparatus, which is called a biorizator, was 
invented by Dr. Oscar Lobeck, in Germany, in 1912. 
The inventor claims that by this process all of the harm- 
ful bacteria are destroyed, while the color, odor, taste, 
albumen, ferments, salts, and cream line are not affected. 
It has been proposed to destroy bacteria in milk by 
subjecting them to the action of ultra-violet rays, elec- 
tricity, and ozone, but the processes in which these agents 
are used have all proved less satisfactory than pasteuri- 
zation. 
