16 
BULLETIN 1344, U. S. DEPARTMENT OF AGRICULTURE 
EFFECT OF PUMPING MILK 
LABORATORY TESTS 
Experiments were conducted to determine the effect of pumping, 
if any, on the creaming ability of raw and pasteurized milk. Four 
types of pumps were installed and milk was pumped through each 
at various temperatures. The following types of pumps were used : 
(1) Rotary pump (about 800 r. p. m.) ; (2) centrifugal pump (about 
1,800 r. p. m.) ; (3) piston pump; and (4) piston pump (valveless). 
The results of these tests are shown in Table 16. 
Table 16. — Effect of pumping milk at various temperatures 
Description 
Temper- 
ature at 
which 
sample 
was 
pumped 
Temper- 
ature to 
which 
cooled 
before 
storage 
Cream volume 
Sam- 
ple 
Control 
sample 
(before 
pump- 
ing) 
Pumped through- 
No. 
Centrif- 
ugal 
pump 
Piston 
pump 
Rotary 
pump 
Valveless 
piston 
pump 
1 
Old raw 
o F 
36 
38 
84 
70 
60 
60 
80 
80 
145 
145 
110 
108 
54 
48 
45 
45 
o K 
38 
38 
46 
46 
60 
46 
80 
46 
46 
46 
46 
46 
46 
48 
45 
45 
14.0 
14.0 
5.0 
10.0 
15.0 
14.0 
15.0 
13.0 
10.0 
12.0 
11.0 
12.0 
12.0 
9.0 
12.0 
8.0 
12.0 
12.5 
6.0 
12.5 
14.0 
13.5 
14.0 
14.0 
13.0 
12.5 
6.0 
11.0 
15.0 
14.0 
14 5 
14.0 
9.0 
11.0 
10.0 
11.0 
10.0 
8.5 
14.0 
13.0 
2 
do 
11.0 
3 
5.0 
10.0 
15.0 
14.0 
14.0 
13.5 
10.0 
11.5 
11.0 
11.0 
12.0 
7.5 
10.0 
4 
Fresh raw... __ 
5 
6 
do.. 
"!-~do~---~"~"~--~-~-~- 
Fresh pasteurized 
7 
8 
9 
10 
10.0 
10.0 
10.0 
11.0 
7.0 
11 
12 
-~-~~do~~I~.~"~"~I~~~-I- 
11.0 
12.0 
13 
14 
15 
do 
Old pasteurized, cooled 
in vat to 108° F 
10.5 
8.0 
12.0 
16 
8.0 
8.0 
8.0 
Sample No. 1 was old raw milk, and pumping it at 36° F. affected 
the cream volume only slightly. Sample No. 4 was the same as No. 1, 
except that the milk was heated to 70°. The control as well as the 
pumped samples had less cream volume than sample No. 1, as did 
also sample No. 3, heated to 84°. 
Sample No. 2 was old raw milk taken from the storage room at 
38°. It will be noted that pumping seemed to have a detrimental 
effect on this milk. The control sample was immediately placed in 
storage and showed a better cream volume than any of the pumped 
samples. 
Sample No. 3 was old raw milk heated to 84° F. The cream layer 
was considerably injured on the control as well as on the pumped 
samples. The cream volume on a sample of this milk before it was 
heated was 14. This corroborates the results in other tests, which 
indicate that agitation of milk at certain temperatures has a detri- 
mental effect on its creaming ability. 
Sample No. 5 was cooled immediately from 80° to 60° F. The 
milk was pumped through the various pumps at 60°, and the samples 
were placed in storage without further cooling. It will be noted 
that a better cream volume was obtained on the No. 5 samples when 
they were not cooled than on the No. 6 samples which were cooled 
