232 cream-ki]'I';ning and starters 



the starterlinc, as high as possible in hot water, say up to about 

 200° F. 'J'he sample may assume a eookerl taste, but this will 

 soon disappear after the starter has Ix-en carrierl on a few 

 days. The milk should be left at this high temperature for 

 about ten or hfteen minutes. A longer time does n(j harm. 

 Then the milk is gradually c(joled to abcjut 80^ F. This high 

 temperature is desirable, because the germs present in the 

 commercial culture may be somewhat dormant. This high 

 temperature would tend to revive them more quickly than a 

 lower temperature. Great care should always be taken to 

 cool the milk previous t(.) inoculating it with the i)ure culture, 

 otherwise the germs present in the culture will be destroyer]. 



Inoculation. — The next step is to inoculate the prepared 

 milk with the culture obtained from the laborat(jry. The 

 bottle which contains the culture is carefully opened, turned 

 over and emptied into the pasteurized milk. It should be 

 held down closely to the mouth of the jar containing the 

 sterile milk, in order to prevent, as far as possible, the entrance 

 of the air and the consequent danger of contamination. Then 

 the milk c(;ntaining the culture is thoroughly stirred and set 

 away in a room where the temperature is about 70*^ F. This 

 will gradually cool the milk from 80'^' to 70^ F., and in about 

 twenty to forty hours the milk will sour and coagulate. Gemis 

 in nearly all of the liquid cultures are rather slow in acting upon 

 the milk, undoubtedly due to the dormancy of the germs, and (.0 a 

 comparatively few of them being present in the culture. When 

 the powdered cultures are used, a little more care is essential to 

 get the powder thoroughly mingled with the milk. It is a trifle 

 more difficult to get the j)owder thoroughl}' mixed with the milk 

 than it is to get the liquid cultures mixed. If anything is used 

 with which to stir the sample, it should be sterilized before com- 

 ing in contact with the milk. This applies in the jireparation of 

 all cultures. Jn testing or sampling the mother-starter, nothing 

 should be allowed to come in contact with it unless it has pre- 

 viously been thoroughly sterilized. The powder cultures are 

 usuall}' more \'igorous in their effect than most of the liquid 

 cultures now c^r the market. The powder cultures usually 



