18 
BULLETIN 1344, U. S. DEPARTMENT OF AGRICULTURE 
included in these tables was 2.3 per cent. At the plants investigated 
pumping raw milk from the weigh can to the receiving vat caused 
only a slight reduction in the cream volume. 
Table 17. — Effect of pumping raw milk at commercial plants 
Test number 
Tem- 
pera- 
ture 
Cream volume > 
Decrease in cream 
volume 
Type of pump 
Control 
Pumped 
Amount 
Per cent 
1 
°F. 
70 
67 
66 
44 
61 
47 
32-46 
70 
33 
43 
64 
60 
63 
14.75 
17.0 
16.0 
14.0 
13.5 
14.75 
13.5 
16.0 
13.5 
12.0 
14.0 
13.0 
16.0 
14.50 
17.0 
16.0 
14.0 
13.5 
14.0 
13.5 
15.0 
13.5 
11.5 
14.0 
12.5 
14.5 
0.25 




.75 

1.0 

.5 

.5 
1.5 
1.7 




5.1 

6.3 

4.2 

3.8 
9.4 
Rotary, 180 r. p. m. 
Centrifugal, 1,500 r. p. m. 
Do. 
Do. 
Piston, 25 s. p. m. 
Centrifugal, 1,500 r. p. m. 
Do. 
Rotary, 180 r. p. m. 
Centrifugal, 1,500 r. p. m. 
Do. 
Piston, 24 s. p. m. 
Do. 
Do. 
2 
3 
4 
5 
6 
7 . 
8 
9 
10. 
11 
12 . . 
13 
Test No. 
Tem- 
perature 
Cream volume 
Increase or de- 
crease in cream 
volume 
Type of pump 
Control 
Pumped 
Amount 
Per cent 
1 
° F. 
149 
129 
120 
120 
115 
115 
115 
11.5 
11.5 
13.5 
13.0 
10.6 
12.0 
15.0 
11.5 
11.5 
i 13.5 
i 13.0 
11.0 
12.0 
15.0 




+0.5 






+4.7 


Centrifugal, 1,500 r. p. m. 
2 
Do. 
3 
Rotary, 180 r. p. in. 
4 
Do. 
5 
Piston, 80 s. p. m. 
6 . 
Do. 
7 
Centrifugal, 1,800 r. p. m. 
i Also filtered. 
EFFECT OF HOLDING MILK AND OF AGITATING IT AT VARIOUS 
TEMPERATURES BEFORE AND AFTER PASTEURIZATION 
The tests on the effect of pumping milk indicated that the tem- 
perature at which the milk was pumped was of much more impor- 
tance than the pumping itself. Tests were therefore undertaken to 
1 In all cases the butterfat of the control and pumped samples was the same. 
EFFECT OF PUMPING PASTEURIZED MILK AT COMMERCIAL PLANTS 
Seven tests were conducted at commercial plants where the milk 
was pumped after pasteurization. The results are shown in Table 
18. It will be noted that there was no reduction in any instance as 
a result of pumping the milk. Sample No. 5 showed a slightly 
greater cream volume after pumping, which was undoubtedly due to 
experimental error. In all cases the butterfat tests of the control and 
pumped samples were the same. Although the number of tests made 
is comparatively small, they plainly indicate that pumping pasteur- 
ized milk at temperatures between 145° and 115° F. has no harmful 
effect on the creaming ability of the milk. The results corroborate 
the laboratory tests shown in Table 16, where it was found that the 
cream volume was only slightly affected by pumping the hot pas- 
teurized milk. 
Table 18. — Effect of pumping pasteurized milk at commercial plants 
