THE CREAMING ABILITY OF MARKET MILK 
23 
to more complaints on the part of the consumer than a slight reduc- 
tion in the cream depth as a result of the various processes in the 
plant. 
Fig. 1. — Effect of various shapes of milk bottle on the apparent cream volume 
SUMMARY AND CONCLUSIONS 
Milk heated to 143° F for 30 minutes showed practically no de- 
crease in the cream volume, and in some cases an increase resulted. 
Pasteurization at 145° to 146° F. for 30 minutes reduced the cream 
volume an average of approximately 8 per cent, with considerable 
variations above and below. 
Pasteurization at approximately 148° F. for 30 minutes caused 
a decrease in cream volume of from 18.5 to 41.7 per cent, with an 
average decrease of approximately 31 per cent. 
The reduction in cream volume due to pasteurization at 145° to 
146° F. was not so marked in the case of 24 to 36 hours old milk as 
in fresh milk, owing to the fact that old milk does not show so deep 
a cream volume before pasteurization as does fresh milk. Pasteuri- 
zation of old market milk had a tendency to restore its creaming 
ability. 
The cream volume results showed only slight variations due to the 
different types of pasteurizing apparatus which were in use at the 
plants investigated, when factors in the processing other than heat- 
ing and holding were not involved. 
At the particular plants investigated there was practically no 
difference in the cream volume results from apparatus using a low- 
temperature heating medium as compared with that using a high- 
temperature medium, provided the time of heating was approxi- 
mately the same. 
Only a slightly better cream volume was obtained in vat pas- 
teurization when a low-temperature heating medium was forced 
through the coils by a direct-acting pump, as compared with the 
ordinary circulation of a heating medium of higher temperature. 
The tests to show the effect of agitation during the holding period 
were not uniform, but the tendency appeared to be slightly in favor 
of holding the milk without agitation during this period. Moderate- 
agitation during the 30-minute holding period apparently has no 
appreciable effect on the cream volume. 
