104 MILK [vi 



fine white velvety appearance. Among the yeasts 

 may be mentioned the saccharomyces lactis, the sac- 

 charomyces acidi lactici, and the saccharomyces ruler. 



Methods of Destroying or Regulating Bac- 

 terial Life in Milk. Before concluding this Chapter, 

 it may be well to say a word or two on the methods 

 we have at our disposal for regulating or for entirely 

 checking the development of bacteria in milk. 



At first sight the task of excluding bacteria from 

 milk, or even regulating their development, seems to 

 be a hopeless one. But this is not so. Perfect 

 sterilisation is not, under present practical methods, 

 possible, nor, indeed, is it of such great importance, 

 although in many cases highly desirable. In the first 

 place, we cannot expect to entirely prevent the 

 entrance of bacterial life to milk in the process of 

 milking. We may, however, by the exercise of 

 scrupulous care, and the observance of cleanliness, 

 minimise contamination. . If milk is dirtily and care- 

 lessly handled, bacteria, with spores possessing ex- 

 tremely resistant properties, are apt to take possession 

 of it, such as those of the butyric, the hay, and potato 

 bacilli, which render subsequent sterilisation by heat 

 an extremely difficult task. 



Sterilisation of Milk. A distinction should be 

 made between two terms which are often used 

 synonymously, viz. sterilisation and Pasteurisation. 

 Perfect sterilisation of milk can only be effected by 



