22 
BULLETIN 1344, U. S. DEPARTMENT OF AGRICULTURE 
Five tests were made at plants where the pasteurized milk was 
filtered. The results are shown in Table 23. 
The control sample was taken just before the milk entered the 
filter, and with the exception of test Xo. 1 the filtered sample was 
taken at the outlet of the filter. 
It will be noted that there was a reduction in cream volume in only 
one instance, test Xo. 1. In this instance the sample was taken 
after it went over the cooler, which may have been the cause of 
the decrease in cream volume. In all cases the milk was filtered 
before it had been cooled below 115° F. These investigations would 
indicate that filtering hot pasteurized milk has little, if any, effect 
on the cream volume. 
Table 23. — Effect of filtering pasteurized milk 
Temper- 
ature 
Cream volume 
Increase or decrease 
after filtering 
Test No. 
Control 
milk 
Pumped 
milk 
Pumped 
and 
filtered 
milk 
Amount 
Per cent 
1__ . 
° F. 
149 
120 
120 
115 
115 
11.5 
13.5 
13.5 
10.5 
12.0 
11.5 
ilO.O 
13.5 
13.0 
11.0 
12.0 
-1.5 




— 13.0 
2 

3 
13.0 
11.0 
12.0 

4 


1 Sample taken after milk went over the cooler. 
INFLUENCE OF VARIOUS SHAPES OF MILK BOTTLES ON DEPTH 
OF CREAM LAYER 
It has been noted that there may be considerable variation in the 
depth of the cream volume in the same milk, if placed in bottles of 
different heights and shapes. In many cities there are no bottle ex- 
changes and the dealers do not have a uniform stock of bottles. 
Some plant owners purposely purchase bottles designed to extend 
the depth of the cream layer, and others apparently do not consider 
this feature. The bottles rapidly become interchanged between deal- 
ers, and as a result each pasteurization plant uses bottles that vary 
considerably in shape and height. 
Figure 1 shows various-shaped milk bottles and the variation in 
the depth of the cream layer which results. Equal quantities of the 
same milk were placed in these bottles and they were allowed to 
stand at a uniform temperature for 20 hours. A measurement of 
the depth of the cream layer is as follows : 
Bottle 1 2i§ inches. 
Bottle 2 3% inches. 
Bottle 3 3% inches. 
Bottle 5 shows an increase in the cream depth of approximately 
22 per cent as compared with bottles Nos. 1 and 4. This is an appar- 
ent variation in cream volume of more than the actual variations ob- 
tained in many of the steps of processing discussed in this bulletin. 
A consumer receiving two quarts of milk, one in a bottle with a wide 
neck and the other in a bottle with a narrow neck designed to extend 
the cream layer, would undoubtedly note the lack of uniformity in 
the apparent richness of the milk. Such variations may give rise 
Bottle 4 2H inches. 
Bottle 5 3t 7 jt inches. 
Bottle (5 3A inches. 
