Bacteria in Butter- Making. 



135 



handled or the cream is pasteurized after separation. 

 The necessity of heating the skim-milk to destroy the 

 seeds of tubercle in the milk- supply makes it advisable 

 to heat the whole milk, thus subserving two purposes by 

 the same operation. 



135. Pasteurizing" apparatus for butter- making*. 

 Most of the European pasteurizing machinery has been 

 devised from the butter-maker's standpoint. They are, 

 therefore, machines that have a large capacity, as this 

 factor is generally regarded as of chief importance in 

 pasteurizing for butter- making. To fulfill this condition, 

 most of them are arranged with a continuous inflow and 

 outflow. Such an arrangement militates considerably 



against the efficiency of any 

 machine as a bacteria- de- 

 stroying agent. In a test 

 made by the writer 1 of 

 Reid's pasteurizer (fig. 31), 

 which is a modification of a 

 Danish machine, it was 

 found that the bacterial 

 content of the pasteurized 

 milk varied greatly, rang- 

 ing from 50-99%, although 

 on the whole the germicidal 

 effect was very marked. 



136. Attributes desir- 

 able in pure culture 

 starters. In adding a pure 



Reid's pasteurizer for butter- culture starter to cream, it 

 is desirable, if possible, to 

 use a ferment that possesses the following character- 

 istics : 



FIG. 31. 

 making. 



1 Wis. Expt. Stat., Bull. 69, p. 11. 



