Bacteriology 15 



Preparation of Larger Amoimts of Starter. 



Determine the quantity of starter required, select 

 the milk as carefully as before, pasteurize, cool and 

 add the mother starter. 



The milk should be pasteurized at a temperature 

 of 180° F. for thirty minutes if possible. A good 

 incubation temperature is 60° to 65° F. However, 

 this temperature may be varied so that the starter 

 will be ready at a given time — the 'higher the tem- 

 perature the less time is required to ripen the 

 starter. 



Pasteurization and incubation can be carried on 

 in a starter can or a milk can. The former requires 

 mechanical power to operate the agitator. The 

 latter may be used where mechanical power is not 

 available, and the milk and starter is stirred by 

 hand. This kind of apparatus is more often used 

 in cheese factories. 



Amount of Mother Starter to Use. 



Use the mother starter prepared the day before. 

 The amount depends upon the following factors : 



1. Temperature of milk when mother starter is 

 added. 



2. Average temperature at which the milk will be 

 kept during the ripening period. 



3. Time allowed for the starter to ripen before it 

 is used. 



4. Vigor and acidity of the mother starter added. 



The amount of starter may vary from 0.5 per cent 

 to 10 per cent, dependhig upon the above conditions. 



Some operators prefer to add the mother starter 

 while the milk is at a temperature of about 90° F., 

 before it has been cooled to the incubating tempera- 



