THE CREAMING ABILITY OF MARKET MTLK 7 
In 19 of the tests at temperatures not over 146° at the beginning 
and not less than 145° at the end of the holding period, 2 showed 
increases of 22.2 per cent and 9.1 per cent, and 2 showed no change, 
while 15 showed decreases ranging from 4.5 per cent to 25 per cent. 
In 6 tests of the butterfat percentage of the under layer at these 
temperatures, 4 showed decreases ranging from 18.2 to 46.6 per cent, 
while 2 showed increases of 15.6 and 36.3 per cent, respectively. 
In four tests at temperatures not over 145° at the beginning and 
not less than 144° at the end of the holding period, all showed de- 
creases in cream volume varying from 3.7 to 57.7 per cent. Three 
butterfat tests of the under layer at these temperatures showed the 
butterfat content decreased 6.1 per cent in one case, increased 7.7 per 
cent in one case, and remained unchanged in 1 case. 
In 13 tests at temperatures of not more than 144° F. at the begin- 
ning and not less than 140° at the end of the holding period, 4 
showed increases ranging from 3.3 to 13 per cent, 4 remained un- 
changed, and 5 showed decreases ranging from 6.3 to 11.1 per cent. 
In 7 tests at these temperatures, 2 of the butterfat percentages in 
the under layer showed increases of 12,5 and 18.2 per cent and 5 
showed decreases ranging from 3.9 to 43.7 per cent. 
The temperature of the heating medium varied from not more than 
155° F. to that of steam at 5 pounds pressure. Although the number 
of tests with the heating medium at various temperatures is not suffi- 
cient to permit definite conclusions to be drawn, with the equipment 
used in these tests the high-temperature medium did not cause any 
greater decrease than a low-temperature medium. There was no 
apparent effect from agitation during heating as ordinarily used at 
the plants ; nor did the time required to heat the milk to the desired 
temperature by the various types of apparatus used at the plants 
have any apparent significance. 
It was noted that in vat or tank pasteurization, in the majority of 
instances, agitation during the holding period under the methods 
described resulted in little or no change in the cream volume as com- 
pared with holding the milk during the 30-minute period without 
agitation. 
EFFECT OF PASTEURIZING FRESH MILK 
Table 4 is a summary of 10 tests made in the laboratory on the ef- 
fect of pasteurizing fresh milk at various temperatures. It will be 
noted that in several cases there was an increase in cream volume 
for milk pasteurized at 143° F. All samples pasteurized at 145° 
showed a decrease in cream volume, with the exception of sample No. 
6, which showed a slight increase. All samples pasteurized at 148° 
showed a marked decrease in cream volume. (Compare with re- 
sults of pasteurizing old milk, as shown in Table 5.) 
EFFECT OF PASTEURIZING OLD MILK 
In Table 5 are seen the results of tests made to show the effect of 
pasteurizing milk 30 to 36 hours old that had been recreamed at 
least once. The raw old milk showed a poorer cream volume than 
raw fresh milk of the same butterfat content, so that the reduction 
from pasteurizing old milk is not so marked as in the case of pasteur- 
izing fresh milk. 
