Il8 MODIFIED MILK AND MILK PRODUCTS 



bacilli in butter. The sediment and liquid are pipetted off from 

 the fat and re-centrifugalised. The sediment is then examined 

 by methods similar to those described under water and milk. 



V. Cheese. 



The changes which occur in cheese ripening appear to be 

 partly chemical, partly bacteriological, the latter being more 

 particularly concerned with the processes which give the different 

 flavours. There appears to be great obscurity and difference of 

 opinion as to the bacteria concerned and the actual parts they 

 play. 



The number of bacteria in cheese is always large, but varies 

 with the age of the cheese. According to Russell 1 the ripening 

 process can be divided into a period of initial bacterial decline 

 soon followed by a period of great bacterial increase, and ending 

 with a period of bacterial decline. 



A large number of different bacteria has been described in 

 cheese, the lactic acid bacteria forming the largest group. In 

 addition gas-producing bacteria, bacteria decomposing casein, 

 moulds, etc., are all numerous. 



From the public health point of view the bacteriological 

 examination of cheese is seldom undertaken, and is of little 

 value. The only examination of any importance is for B. titber- 

 atlosis. Hormann and Morgenroth found tubercle bacilli in 3 

 out of 15 samples, Rabinowitsch in 3 out of 5 samples, and Eber 

 in 2 out of 50 samples. 



Tubercle bacilli may also live for some time in cheese. 

 Using milk artificially inoculated with tubercle bacilli and then 

 made into cheese, Galtier found the bacilli alive in cheese 

 2 months and 10 days old. Harrison made cheese from milk 

 artificially inoculated with tubercle bacilli. In cheese made by 

 the Emmentaler method, they died between the 34th and the 

 4<Dth day; in Cheddar cheese, after 62 to 70 days. 



Mohler, Washburn and Doane 2 have shown that tubercle 

 bacilli may live for even longer periods. In their experiments 



1 Agric. Exp. Station, Wisconsin, \^th Annual Report, 1896, p. 105. 



2 Annual Report, Bureau of Animal Industry, U.S.A., 1909. 



