EXPERIMENT STATION BULLETINS. 



355 



ACID PRODUCTION IN MILK. 



At both temperatures, we notice plainly the increase of the active 

 mass in the beginning of the fermentation, resulting in an increasing 

 angle of elevation. This continues till the acidity of about 50° is 

 reached, then the curve begins to turn the other way. The point of in- 

 flection indicates the moment when the bacteria cease to increase. In 

 our curve, we can readily see that in the milk at 35°C., the maximum 

 number of lactic bacteria must have been reached about 9 hours after 

 inoculation; in the other sample, about 14 hours. 



Another example of a combination of two fermentations is illustrated 

 in the black line of Figure 7, representing the acid production and de- 

 struction in market milk exposed to the air in a dish with large sur 

 face. The titrations on 20 successive days gave the following degrees 

 of acidity: 



Fig. 6. The Lactic Fermentation. 



