174 BUTTER-MAKING. 
method of pasteurization the substance pasteurized is exposed 
only to a sudden temporary heat. 
The intermittent process of pasteurization tends to drive 
off more of the undesirable taints present in the milk or cream. 
This is especially true when stirred occasionally. If heated too 
long the cooked flavor is likely to be more pronounced than 
when the intermittent system is used. If exposed very long 
Back Pressure Valve 
Skim Milk Inlet 
— =—= 3 
Ai 
Skim Milk Tank i! | 
am UN, 
Exhaust Steam 
Fic. 115.—Scheme for pasteurizing skim-milk by the use of exhaust-steam 
direct. (Creamery Journal, by W. P. McConnell, Minn.) 
to the high temperature and stirred excessively during the 
intermittent pasteurization, the butter-fat tends to melt and 
run together, and show itself on the top of the cream in the 
form of an oily layer. 
2. The continuous method of pasteurization is more practical 
for large amounts of milk or cream. It is used almost without 
exception in pasteurizing cream, whole milk, and skim-milk 
at creameries. Neither one of the two systems destroys spores. 
The. intermittent system is the most effective because botb 
