Bacteria and Butter Making. 149 



of living bacteria. It has been found by experiment that 

 this is at the time the milk curdles at ordinary tempera- 

 ture, or when the acidity is about 0.6-0.7 per cent. If 

 the acidity. is allowed to increase to 0.8 or 0.9 per cent, 



FIG. 31. BOTTLE FOR MOTHER STARTERS. 



A milk bottle with a tumbler for a cover and "a spoon for in- 

 oculating the other bottles enables the butter maker to 

 propagate the starters without contamination. 



the number of bacteria will be less and a larger amount 

 of the starter must be used in order to ripen a definite 

 amount of cream in the desired time. The use of an 

 overripe starter may also have an injurious effect on the 

 flavor. 



The ripened starter should be perfectly homogeneous, 

 showing no bubbles of gas or free whey ; the odor should 

 be agreeable and the acid taste mild; on shaking, the 

 curd should break up into a smooth, creamy liquid free 

 from lumps. This is especially important in the starter 



