PASTEURISATION OF MILK AND CREAM. 57 


effect in diminishing the creaming property of the milk, the 
latter being more affected by the temperature employed. 
As regards the keeping quality of milk pasteurised at 
140 F., it was found by a series of tests that there was prac- 
tically no difference in the keeping quality of milk heated to 
that temperature for either 15 or 30 minutes, and milk- 
heated to 155° F. for 15 minutes. These results were further 
confirmed by a bacteriological examination of the pas- 
teurised milk. 
A number of trials were also made to test the effect of 
heating on the “ body” or consistency of the cream, and the 
results showed practically no difference between the con- 
sistency of normal raw cream and that heated to 140° F. for 
30 minutes. 
The authors conclude their report on these experiments 
with the following observations :—“ The temperature recom- 
mended for the pasteurisation of milk and cream in the past 
MasmceimnS ak for ay period of 15 to, 20 minutes. Dhis 
limit was chosen because it had been regarded as the point 
at which the tubercle bacillus is destroyed in a moist 
medium. When, however, cream or milk is heated to a 
temperature of 140 F., or above, the physical condition of 
the fat globules is changed so that cream appears much 
thinner, and milk loses its property of rapid creaming. This 
objection can be overcome, as is shown by the preceding 
experiments, if milk or cream is not heated above this 
temperature.” 
‘“Not only is the creaming property of the milk and the 
‘body’ or consistency of cream unaffected, but the keeping 
quality is practically as good as it is where the product is 
heated to a temperature of 155’ F. All that is necessary to 
secure good keeping quality is to destroy the vegetative 
bacteria, and as this is accomplished at the temperature of 
140° F., if the exposure is made for a sufficient period of time, 
no advantage in this respect is to be gained by heating to a 
higher temperature. This being true, it only remains to 
determine with certainty how long an exposure must be 
made to destroy the tubercle bacillus. The temperature limit 
that has heretofore been considered necessary where the 
