420 



STATE BOARD OF AGRICULTUI^E. 



TABLE III. 

 Test CvUurea from Table II. 



From Tables II and III, the conclusion may be drawn that the coccus 

 alone does not favor the retention of the vitality of the lactic bacterium 

 nor docs it seem to have any influence either on the acid production of 

 the lactic bacteria or upon the time of curding as determined by the test 

 cultures from the mixed cultures of the three organisms in comparison 

 with those of the lactic organism plus the yeast. For these reasons 

 the coccus may be considered a negligible factor in the retention of 

 the vitality of the lactic bacteria. 



Expt. II. 



Acid Reduction of Yeasts in Pure Culture. 



It is a well known fact that a lactic bacterium will continue to live 

 and produce acid within certain limits if the acid is destroyed or neu- 

 tralized by the addition of alkali in some form. The preservation of 

 the vitality and activity of the lactic bacteria in the mixed culture was 

 therefore attributed to a probable acid-destroying or neutralizing prop- 

 erty of this yeast. 



In order to determine whether this red yeast was an acid-reducer, it 

 was compared with three other yeasts known to be such, a scum yeast 

 from brine pickles "DR", a butter yeast "SC" and a .yeast from whey 

 "DG." The acid reducing power was tested out in pure culture first, 

 by inoculating with the several yeasts, flasks of whey made approxi- 

 mately +30°, +50°, +70° and +90° acid by the addition of N/1 lactic 

 acid. These flasks were sterilized after the addition of the acid. The 

 whey became somewhat turbid when the acid was added but not enough 

 to prevent observation of the growth of the yeast. Each flask of the 

 group of four whey flasks having the approximate acidities of +30°, 

 +50°, +70° and +90° respectively was inoculated with 1 cc. of a broth 

 culture of one of the yeasts. These flasks were titrated from time to 

 time to determine the acidity and the rate of reduction. The following 

 table shows the relative acid reduction of the four yeasts: 



