426 



STATE BOARD OF AGRICULTURE. 



"2 4 6 8 :0 li 'S' 20 



, Coiti>n.i.-,«ll!d With b«*l»:>» 



Curve IV. 



The titration records of these mixed cultures in whey and in milk 

 show a gradual rise in acidity, reaching its maximum in from 20 to 

 30 days, then begins the destruction of the acid. Several of these 

 cultures became contaminated because of the frequency of titrations and 

 these may have influenced the curves in some cases, but a general idea 

 of the action of these yeasts upon the several lactic bacteria in com- 

 bined culture may be obtained from the above charts. 



An effort was made to determine whether the acid produced by the 

 lactic bacteria was merely neutralized in the mixed culture or whether 

 it was decomposed to CO., and H.O by the activity of the yeasts. Quan- 

 titative analyses of several of the mixed cultures was made for the 

 determination of the amount of lactic acid present after the acidity 

 had been reduced considerably by the yeast. Because of lack of com- 

 plete data, the results could only be estimated but they were accurate 

 enough to prove that the acid was destroyed by the yeasts and not 

 simply neutralized. 



As checks on the above mixed cultures, pure cultures of each of the 

 lactic bacteria and of the yeasis wore made in whey and titrated fre- 

 quently. These data are found in the following table: 



