623 
Experiment No. 14. 
Quart mixed market milk. 
Bottle immersed in water 4 inches, 5 inches out. 
No cream line. 
Water 
temper- 
ature. 
Milk temperature. 
Time. 
Colonies 
per loop 
in agar. 
Remarks. 
T,op. 
Bottom. 
° C. 
°C. 
° C. 
Minutes. 
22 
13 
5, 760 
30 
15 
2 
40 
18 
4 
50 
22 
' 5 
60 
27 
8 
70 
32 
8’ 
80 
39 
10 
90 
• 47 
, 12 
95 
50 
13 
. 
14 
Boiling. 
100 
55 
14 
8,000 
100 
60 
15 
14.000 
100 
65 
16 
4, 000 
At 66°, scum. 
100 
70 
18 
389 
100 
73 
19 
Scum. 
COMMERCIAL PASTEURIZATION. 
The commercial pasteurization of milk leaves much to be desired, 
but .although it is not always thoroughly carried out, it is by no 
means a fraud. With a little sanitary supervision on the part of 
health officers and education on the part of those in charge the process 
may be made efficient. 
Commercial pasteurizers are popular with dairymen, not because of 
the public health aspect, but on account of the economic advantages 
in improving the keeping qualities of the milk. It is estimated that 
the expense of a pasteurizer would be paid for in the course of about 
a year. This estimate is based mainly on the saving of losses from 
sour milk. The cost of pasteurization is about one-tenth to one-half 
cent a quart. 
In order to satisfy public health requirements pasteurizers must 
be efficient in operation, permitting a definite quantity of milk to be 
heated to a definite temperature for a definite time (Russell). They 
must be easy of control, the milk must be heated uniformly through- 
out, the apparatus must be simple in construction, easily cleaned, eco- 
nomical in use, and arranged to safeguard against reinfection of the 
milk. Finally, provision must be made for rapid cooling. Given 
an apparatus of proper construction more depends upon the intelli- 
gence and care with which it is run than upon the machine. No pas- 
teurizer is automatic. For instance, I have found that the milk 
pasteurized in a standard machine contained many more bacteria 
