18 



FERMENTING POWER OF PURE YEASTS. 



PURE YEASTS USED SEPARATELY AND IN MIXED CULTURES. 



From many comparative tests of pure yeasts sown in the same 

 must or fruit juice a set of 7 pure sowings and 1 mixed sowing is 

 selected to illustrate the difference in activity which may be shown 

 by pure and mixed yeasts. These tests are taken from a set of 11 

 flasks, which were sown at the same time under identical conditions 

 and all kept under observation in the culture oven. The graphic record 

 presented in fig. 4 includes 3 yeasts from French, 1 from German, and 

 3 from American sources, and gives the entire range of variations de- 

 veloped in this experiment. 



The flasks contained 400 cc each of filtered and sterilized apple juice 

 and were sown with 1 drop on a platinum loop, the mixed cultures re- 

 ceiving 10 drops, i. e., 1 drop from each of the pure cultures used in 

 the experiment. The yeasts used were from the following sources: 

 Nos. 8, 37, and 40, obtained from French Normandy cider, isolated by 

 the writer at Geisenheim, Germany ; No. 53, a quite famous wine yeast, 

 isolated at the royal Prussian laboratories at Geisenheim, Germany, 

 from Steinberg wine; No. 66, from Yellow Newtown cider; No. ( )4, 

 from Hyslop crab-apple juice; No. 100, from the same source as No. 

 94. The last three yeasts were isolated in the mycological laboratory 

 at Blacksburg, Va. No. 100 is the organism known as Saccharomyces 

 <ij>'t> -uhittift, which is always present in abundance in normal fruit 

 juices. The chemical data of the experiment are set forth in the fol- 

 lowing table: 



TABLE III. Chemical analyses of original must and of the same after fermenta- 

 tion with different yenxtx -h<'i>ii<-<il <lrixirtment. Vin/hiiu A uricultunil Experi- 

 ment Station). 



f Grams per 100 cc.] 



These analyses show that all of the organism.-, oxcept No. 100, 

 gave fairly uniform results, with the exception of the data for the 

 percentage of alcohol in the fermented liquor. It is indeed rema rk- 

 able that the alcohol produced should vary more than 1 per cent, 

 but like results have been shown repeatedly in the tests of pure 

 yeasts. In the writer's opinion, this is not an adventitious occur- 

 rence, but a special investigation must be made before attempting a 



