KKLATION OF BACTERIA TO BUTTER 99 



insure plates with a desirable number of colonies, so that all 

 forms present shall have an opportunity to develop. 



From liquid starters plates are prepared as in testing the 

 purity of a culture (p. 31). A portion of the dry starter may 

 be transferred to sterile water by dipping the platinum loop 

 into the water and then into the powder, in which case the 

 moisture will cause a considerable amount of the powder to 

 adhere. From the water blank which has been well shaken 

 after addition of the powder, plates are made in the usual 

 way. 



The plates should be carefully studied, the different types 

 of organisms isolated, and a detailed study made of each. 



It should be remembered that a dry commercial starter is 

 not necessarily to be condemned because it is not absolutely 

 pure. When propagated the lactic organism will, if properly 

 chosen, develop so much more rapidly than the contaminat- 

 ing organisms that these will not exert any continued effect 

 in the starter or in the cream. 



Vitality and fermentative power. In order to be desirable 

 for starter purposes, an organism must grow rapidly when 

 inoculated into milk, which is then kept at temperatures 

 ranging from 20 to 30 C.; it must also produce acid rapidly, 

 and in sufficient amounts for the production of the desired 

 degree of flavor, and to insure exhaustive churning. 



Since the organisms in the starter as purchased may be 

 few in number and weakened by desiccation or by the ac- 

 cumulation of acid, these points should not be determined 

 by means of cultures inoculated directly from the original 

 package, but the organisms should be brought to a normal 

 state of vitality by inoculating sterile milk from the original 

 starter and incubating for twenty-four hours. From this pre- 

 pare a second culture, and from this, after twenty-four hours' 



