474 BOARD OF AGEICULTUKE. 



temperature, in which a rise (from 60 degrees F., and not to exceed 100 

 degrees F.) induces growth and develops immense numbers of bacteria; 

 while lowering the temperature retards growth. The action of these 

 germs in cream results in the conversion of a part of the mills sugar into 

 lactic acid, and a slight formation of carbonic acid gas and a few other 

 volatile constituents not definitely known. 



The production of lactic acid causes the sourness of cream, and is 

 largely accountable for the desired flavor in butter. It is the most im- 

 portant product formed, and serves as a guide in testing the ripeness of 

 cream. The carbonic acid gas is mostly given off, but the volatile constitu- 

 ents play an important part, if the ripening be properly carried on, in 

 producing a fine aroma, which is not obtained when foreign acids are 

 added to sweet cream in the attempt to secure the same flavor without 

 ripening. For this reason sweet cream butter has very little flavor, and 

 •it is only through the ripening or souring of cream that the flavor of but- 

 ter is obtained. The ripening of cream may develop good or bad flavors, 

 depending upon the kinds of bacteria which take part in the fermenta- 

 tion. A particular kind of bacteria, as a rule, gives rise to a fermenta- 

 tion characteristic of that species and consequently the fermentations 

 that give rise to a bad flavor are always due to some undesirable germs 

 that have gained access to the milk. The source of these last named 

 germs in the milk is filth, due to careless and dirty milking or to the 

 use of unclean utensils, or sometimes to the use of milk from a diseased 

 cow. Filthiness is the great source of trouble in the art of butter-making, 

 so much stress must be laid on cleanliness in every phase of milk and 

 butter production. 



Besides bad fermentations, there is another cause of poorly-flavored 

 butter. This comes from cream or milk having been exposed to foul 

 odors, which are absorbed and given to the buttei*. The theory that milk 

 does not absorb odors when warm and cooling has long been abandoned. 

 Experiments show that milk in that condition is even more susceptible 

 to odors than in any other state. In the ripening process this odor can be 

 partly eliminated by aeration or by pasteurization of the cream, but in 

 case of a bad fermentation some antagonistic germ must be added in 

 order to check the progress of the undesirable one. 



This antagonistic fermentation is commonly known as a starter, and 

 if properly prepared contains the right kind of flavor-producing bacteria. 

 The preparation of a starter is as follows: Select three or four pint jars 

 of the best milk that comes to the creameiy, or, where opportunity af- 

 fords, select the milk from several good cows; cover these jars and set them 

 away in a warm place until the milk has coagulated. From these select 

 the one that has developed the best sharp, acid taste, free from disagree- 

 able odors and gas bubbles, and that shows a solid curd. A can of skim 

 milk should then be heated to a temperature not exceeding 175 degrees F. 

 for twenty minutes and cooled to 75 or 80 degrees F. The selected jar 



