THE CREAMING ABILITY OF MARKET MILK 
21 
EFFECT OF CLARIFYING RAW MILK 
In Table 22 are shown the results of clarifying milk at commercial 
plants. The control samples from which the differences in cream 
volume are computed in this table were from the raw milk just prior 
to entering the clarifier. In some instances it had been pumped, de- 
pending upon the routine practice at the particular plant. The re- 
sults indicate that clarification of raw milk at a temperature of ap- 
proximately 60° F. does not materially affect the cream volume. Of 
nine samples clarified at 60° F. to 64° F., four showed no change in 
cream volume, while the other five showed decreases ranging from 
3.6 to 7.7 per cent, the average decrease for the nine tests being 3.6 
per cent. This slight decrease in itself would be of practically no 
commercial importance, but it is a contributing factor ; and, if added 
to other steps in the processing which also decrease the cream vol- 
ume, it must be recognized as important. 
Table 22. — Effect of clarifying rate milk at commercial p7a>?fs 
Test No. 
Temper- 
ature 
Control milk 
Clarified milk 
Increase or decrease 
in cream volume 
Increase or 
decrease in 
butterfat 
of under 
layer 
Cream 
volume 
Butter- 
fat 
Cream 
volume 
Butter- 
fat 
Amount 
Per cent 
1 
2 
3 
° F. 
62 
62 
64 
60 
62 
46 
64 
64 
88 
88 
47 
46 
70 
60 
64 
14.0 
13.5 
14.0 
13.0 
14.5 
14.0 
14.0 
16.0 
12.5 
13.5 
14.0 
13.5 
15.0 
13.5 
13.0 
Per cent 
3.6 
3.7 
3.7 
3.8 
14.0 
13.5 
13.0 
12.0 
14.5 
13.0 
13.5 
15.0 
11.5 
11.0 
13.5 
12.5 
14.0 
13.5 
12.0 
Per cent 
3.6 
3.7 
3.7 
3.8 


-1.0 
-1.0 

-1.0 
— . 5 
-1.0 
-1.0 
-2.5 
— . 5 
-1.0 
-1.0 

-1.0 


-7. 1 
o' 
-7.1 
-3.6 
-6.2 
-8.0 
-18.5 
-3.6 
-7.4 
-6.6 

Per cent 
Not tested. 
Not tested. 
Not tested. 
4 
5 . 
Not tested. 
Not tested. 
6 
7... 
3.9 
3.8 
3.5 
3.5 
3.5 
3.95 
4.0 
3.65 
3.7 
2.7 
3.85 
3.7 
3.6 
3.5 
3.5 
3.9 
4.0 
3.65 
3.7 
3.7 
+14.3 
Not tested. 
8 
9. 
+33 
+33 
10 
Not tested. 
11 
+10 
12 
+18.1 
13 
+22.2 
14 

15 
+6.6 
Only two tests were made at plants where the milk was clarified 
at 88° F. At these two plants the cream volume was decreased by 
8.0 and 18.5 per cent, respectively. 
It is impossible to draw definite conclusions from so small a 
number of tests, but the results of those that were made indicate 
that there is only a slight decrease in cream volume when milk is 
clarified at approximately 60° F. or below, whereas at the higher tem- 
peratures there is more danger of injuring the cream volume. 
EFFECT OF FILTERING MILK 
Mechanical filters to remove the insoluble dirt from milk have been 
developed to a considerable degree in the past few years. At some 
plants the milk is filtered before pasteurization, although the more 
common practice is to filter it after it has been heated to 145° F. or 
after it has been heated and held. 
Only one test was made at a plant where the raw milk was filtered. 
At this plant the milk was preheated to 70° F. before being pumped 
through the filter. A sample taken between the pump and filter 
showed a cream volume of 14.5, whereas a sample taken at the outlet 
of the filter showed 14, or a reduction of only 3.4 per cent. 
