BUTTER-MAKING 247 



milk should be thoroughly sterilized. In creameries where large 

 quantities of cream are handled, the amount of starter needed 

 is quite large, and a starter can be made most satisfactorily 

 in the starter cans made especially for the purpose. These 

 cans are so constructed that the skimmed milk can be sterilized 

 in them, then cooled to the proper temperature, the mother 

 starter added, and the desired temperature for development 

 maintained. In the use of starter, care should be taken to see 

 that it has developed to the point at which the bacteria have 

 their greatest activity, which condition exists just after the 

 starter has become completely coagulated ; if it is too old, the 

 bacteria are weakened by the presence of the lactic acid. An 

 over-ripe starter does not give satisfactory results in cream 

 ripening, and should not be used. 



The butter-maker cannot give too much attention to the 

 quality of his starter, for while a good one is of material aid 

 in producing butter of uniformly good quality day by day, the 

 use of a poor one will just as surely result in injuring the 

 quality of the product. 



Temperature for ripening cream. — The bacteria which 

 produce lactic acid grow most rapidly at temperatures of about 

 80° to 95° F. Other species which produce undesirable changes 

 in the cream also grow rapidly at this temperature. The object 

 sought in the ripening process is the greatest development 

 of the acid-producing organisms relative to the other species 

 which may be present in the cream. It has been found that 

 this result is best obtained by ripening the cream at tempera- 

 tures from 60° to 70° F. The acid bacteria will develop at 

 temperatures below 60°, but their growth is much slower both 

 actually and relatively compared with certain other species 

 which are not desirable. Under certain conditions it may be 

 desirable for the butter-maker to use temperatures higher or 

 lower than the above, but under normal conditions, the use 

 of these temperatures will give the greatest relative develop- 



