196 DAIRY FARMING 



Preparation. Most of the commercial cultures are 

 sent out in one-ounce bottles which are hermetically 

 sealed. The method of making starters from them is 

 the same for all whether they are obtained in the liquid 

 or in the dry form. 



In making the first batch of commercial starter, the 

 entire contents of the bottle is put into a quart of skim- 

 milk, sterilized by keeping it at a temperature of 200 

 F. for two hours, and then cooling to 80 which tem- 

 perature should be maintained until the starter has thick- 

 ened. A new starter is now prepared by introducing the 

 quart of starter into about forty pounds of skim-milk, 

 pasteurized by keeping it at a temperature of 170 to 185 

 for thirty minutes and then cooling to 65 F. All sub- 

 sequent starters are prepared in the same way except 

 that the amount of mother starter for inoculation must 

 be reduced a little for a few days because the germs 

 become more vigorous after they have propagated several 

 days. 



The first and second starters prepared from a new 

 culture seldom have the good flavor produced in sub- 

 sequent starters. The cause of this in all probability 

 is the inactive condition of the germs and the peculiar 

 flavor of the medium in which they are sent out. 



RENEWAL OF STARTERS. 



Under average farm conditions it is policy to 

 renew the starter at least once a month by purchasing 

 a new bottle of culture. It will be found that after the 

 starter has been propagated for two or three weeks bad 

 germs will begin to, manifest themselves as a result of 

 imperfect pasteurization, contamination from the air, or 



