PASTEURIZATION OF MILK AND CREAM 107 
teria cannot be obtained unless the milk is heated to 
176° F. But a stream of milk coming from a flash 
machine and showing a temperature of 176° F., does not 
necessarily mean that every particle of the milk is heated 
to this temperature; indeed, quite the contrary is to be 
expected. It is easily conceivable that where milk passes 
through a machine in a constant stream, some particles 
i rn 3 176 
atiigsecatere! 
167° 
158° 
i HH t ASAE 
: fen '49 
Es- "4 
ee 
rT 
q 
P= ee | 
it 
ai 
al f 
11 { 
Lt I 
io” 30° 30° 40° 50° 60 
Fig. 39.—Chart by Dr. North. 
will be heated higher than others, that is, some particles 
will exceed 176° while others will fall short of this tem- 
perature. It is generally conceded that perfectly uniform 
heating is practically impossible with the flash process, 
and for this reason it is perfectly possible for some 
bacteria with a thermal death point of 176° F., or even 
lower, to. escape destruction by this process. 
