DISCUSSION OP TESTS. 15 



The notes continued throughout the experiment in the same tenor 

 and showed clearly the striking differen. -e- apparent in the character 

 of the liquors. It is very evident, from this and numerous other i 

 made, that dominant fermentation with pure yeast will not dt-n-oy 

 the troublesome organisms present, but will control the fermentation 

 for a certain period and, as was shown in the ca.-k experiments ( Bul- 

 letin 88), it renders practical control fairly simple when the liquor 

 is racked and handled at proper temperatures. In fact, it is possible 

 to almost or quite eliminate the acetic and other troublesome ferment- 

 by proper attention to details and control of the temperature. When 

 the first fermentation is accomplished, at a comparatively high tern 

 perature (75 to 80 F.), the liquor must be promptly racked and 

 handled under control from outside contamination to prevent the de- 

 velopment of the acetic ferments. 



EFFECT OF VARYING QUANTITIES OF YEAST ON RAPIDITY OF FERMENTATION. 



Dry yeasts will not prove desirable in the fermentation industries 

 because they must first be brought into active growth before they 

 will prove efficient as "starters," and present experience indicates 

 that their handling by ordinary methods will, without doubt, result 

 in contamination. 



It appears, therefore, that the active culture prepared by sowing 

 a pure yeast into sterilized must is the only proper inoculating mate- 

 rial for the fermentation of fruit juices. 



In the cask work described in Bulletin 88 one pint of sterilized 

 must fermented with a pure yeast culture was sown to 50 gallons of 

 fresh fruit juice, just from the press, or 1 part of starter to 400 

 parts of must. This, in every instance, produced a strong fermenta- 

 tion, which appeared readily to dominate and prevail over the or- 

 ganisms present in the natural must. This quantity of yeast culture 

 having proved efficient on a large scale, the same proportion was used 

 in the laboratory experiments for the control of unsterilized must 

 The recommendation sent out from the German laboratory at Geis- 

 enheim directs the use of 1 part of fresh yeast culture to 250 or 300 

 parts of must. This practice should be varied according to condi- 

 tions; so large a proportion is not necessary under the best condi- 

 tions of temperature in cellars or fermentation rooms, but where the 

 conditions are not good, 1 part to 100 should be used for safety. 



An experiment bearing upon this point was conducted by the 

 writer in the laboratory at Geisenheim, Germany, and the results are 

 presented in 'fig. 3. The purpose of this test is to show the effect 



U. S. Dept. Agr., Bureau of Chemistry, Bui. 71, p. 



