220 BUTTER-MAKING. 



containing the milk into cold water, covering the jar so as 

 to prevent outside contamination, and then heat up the 

 water gradually. Care should be taken not to insert these 

 bottles suddenly into scalding hot water, or to let the steam 

 strike them, for either is likely to crack the bottles. Care 

 should be taken also to exclude water from milk used for 

 starters. It is advisable to heat this milk, for the starterline, 

 as high as possible in scalding water, say up to about 200 F. 

 The sample may assume a cooked taste, but this will soon 

 disappear after the starter has been carried on a few days. 

 The milk should be left at this high temperature for about ten 

 or fifteen minutes. A longer time does no harm. Then the 

 milk is gradually cooled to about 80 F. This high temperature 

 is desirable, because the germs present in the commercial cul- 

 ture 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 to 

 inoculating it with the pure culture, otherwise the germs present 

 in the pure culture .will be destroyed. 



Inoculation,- The next step is to inoculate the prepared 

 milk with the pure culture obtained from the laboratory. The 

 bottle which contains the pure culture is carefully opened, then 

 the bottle containing the culture is turned over and emptied 

 into the pasteurized milk. The bottle should be held down 

 closely to the mouth of the jar containing the sterile milk, in 

 order to prevent too much contamination from the air. Then 

 the milk containing the pure 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. 

 Germs in nearly all of the liquid cultures are rather slow in 

 acting upon the milk, undoubtedly due to the dormancy of the 

 germs, and to a comparatively few of them being present in 

 the pure culture. When the powdered cultures are used, a 

 little more care is essential to get the powder thoroughly min- 

 gled with the milk. It is a trifle more difficult to get the 



