154 SCIENCE AND PRACTICE OF CHEESE-MAKING 



like a clear or satisfactory presentation. It is quite 

 probable that some of these enzyms, now described 

 under different names, are the same or are mix- 

 tures. The quantity of these substances is so ex- 

 tremely small and the methods of separating them 

 in pure form are so imperfect that their study pre- 

 sents peculiar difficulties. One of the main prac- 

 ; tical uses to which enzyms in milk have been put 

 ' depends upon the fact that their presence serves to 

 distinguish unheated from boiled milk, because the 

 enzyms are all destroyed by heat. We shall not 

 consider these substances in detail ' because, so far 

 as we now know, most of them are not concerned 

 in cheese-making. Galactase is the only one of special 

 interest in this connection. This was discovered at 

 the Wisconsin experiment station in 1897 and has 

 received considerable attention in connection with 

 studies of milk and cheese. We shall consider this 

 enzym in more detail later (p. 297). 



