CREAM-RIPENING 



211 



so that when cream is ripened properly, it contains few other 

 germs besides those which produce lactic acid. 



From the above it will be seen that there are practically two 

 overlapping periods in the bacterial changes during the ripening 

 of the cream, and especially is this so in the ripening of raw 

 cream. The first includes the period when all the different 

 varieties of germs grow, and the second includes the period 

 when only the lactic-acid-producing germs grow. It is, there- 

 fore, maintained that before the churning takes place the 

 ripening of cream should be carried on to such an extent that 

 the lactic-acid germs only predominate. Dr. Storch, who has 

 made a detailed study of this, asserts that milk and cream 

 both have a rather undesirable flavor at the beginning of its 

 ripening period, while in the latter stage of the ripening period 

 it takes on a pleasant, clean, acid taste. 



The number of germs, and the relative number of acid-pro- 

 ducing germs in the cream when ripened, is as shown in the 

 following table : * 



Eckles found that when good- flavored cream is ready for 

 churning the number of bacteria per cubic centimeter varies 

 from 380,000,000 to 3,000,000,000. Of this number the acid- 

 producing bacteria constitute from 91% to 98%. 



Chemical Changes. The changes in cream during the process 



* Bui. 40, Iowa Experiment Station. 



