I2 4 



MILK AND DAIRY PRODUCTS PART 



THE FERMENTATION TEST WITH MILK. 



A simple test which can be used to ascertain whether a milk 

 is normal or faulty in a bacterial sense is that based upon the 

 changes which it undergoes when kept at a temperature of 

 38-40 C. Under these favourable conditions the straggle for 

 existence amongst the bacteria is clearly indicated by the 

 appearance of the milk at the end of a certain number of hours. 



FIG. 53. Apparatus for the Fermentation Test. 



This can be made to serve as a test of the bacterial 

 properties of the milk. The method in its present form is due 

 to Walter, and only requires a simple apparatus such as that 

 shown in Fig. 53. 



The cylindrical test tubes, which fit into a metal stand, 

 are furnished with caps of metal or rubber. The tubes are 

 either large, holding 120-140 c.c., or small, holding 40-50 c.c. ; 

 the larger are to be preferred, for in them the test is more 



