148 Dairy Bacteriology. 



it should be as fresh and clean as it is possible to obtain. 

 The clean bottle should be filled half to two-thirds full, 

 covered and heated in some manner so that the milk 

 shall be at a temperature close to the boiling point for 

 fifteen to twenty minutes. The heating may be done 

 by placing the bottles in water, which is heated on a 

 stove or by steam, or the bottles may be subjected to 

 streaming steam. The milk is cooled quickly and the 

 contents of the package purchased added and well mixed 

 with the milk. In the case of the dry starters, the mix- 

 ing should be done with especial care. The bottle is kept 

 in a warm place and in twenty-four to thirty-six hours, 

 the milk should be curdled. A second bottle must be 

 treated as before and inoculated from the first, and the 

 process repeated daily since the bacteria must have fresh 

 food, if they are to be maintained in good condition. 



In order to accomplish this, the maker must be able 

 to maintain constant conditions from day to day, espe- 

 cially with reference to the amount of the ripened 

 starter that is transferred to the fresh bottle of milk, 

 and the temperature at which the bottles are kept. A 

 spoon, arranged as shown in Fig. 31, enables one to 

 carry a definite amount of the ripened starter to the 

 bottle of milk to be inoculated and a constant tempera- 

 ture box (Fig. 32) permits of the maintenance of the 

 same temperature from day to day. Through careful 

 supervision of these points, and by taking care at every 

 step to avoid the introduction of contaminating organ- 

 isms, the purity of the culture can be maintained, and 

 the bacteria kept in a healthy condition. 



The starter is used because of the acid-forming bac- 

 teria it contains ; it is said to be ripe and in the best con- 

 dition for use at the time it contains the greatest number 



