Bacteria and Butter Making. 143 



whether the product was uniform from day to day, but 

 with the advent of the modern creamery, turning out 

 thousands of pounds of butter per day, and with the ex- 

 tension of the markets for the product, the question of 

 uniformity came to be of much importance. A uniform 

 product can be secured only by the control of the type 

 of fermentation in the cream, or by the control of the 

 kinds of bacteria that cause the souring of the cream. 

 Modern methods of butter making have been devised on 

 the basis of an improvement in the ripening process. 



Starters. From the earliest practice of allowing the 

 cream to stand until sufficient quantity had accumulated 

 for churning, it was only a step, but a most important 

 one, to the addition of sour milk, sour cream, or butter 

 milk, to hasten the ripening process. This was the be- 

 ginning of the modern starter. Experience demon- 

 strated that the addition of these already fermented liq- 

 uids exercised a desirable effect upon the production of 

 butter flavor, even though, at that time, the phenomenon 

 of milk fermentation was not satisfactorily understood, 

 and the relation of bacterial by-products to the produc- 

 tion of flavor in butter was not recognized. 



As a result of experience alone, improvements in the 

 development of the "home made" starter took place. 

 By careful selection of clean milk, and the natural fer- 

 mentation of this under carefully controlled conditions, 

 as well, as the control of the temperature of the cream 

 during the ripening, improvement in the technique of 

 cream ripening gradually developed. More and more 

 attention was given to the preparation of the starter, 

 and its propagation from day to day, under conditions 

 which would prevent its deterioration. This method of 

 utilizing naturally fermented milk or cream was gra- 



