DISCUSSION OF TI.STS. 



13 



the use of pure yeasts for securing dominant lei-mentation in un- 

 sterili/ed must is of great importance in the manufacture of bever- 

 ages and vinegar from fruit juices. The difficulties which constantly 

 arise in the fermentation rooms or in the vinegar factory are many, 

 and any practicable method of insuring a strong, active fermenta- 

 tion which will overcome the various malferments that cause trouble 

 and disease in the fermenting must will be valuable. The expcri 

 ments previously made and the analyses of the products obtained 

 clearly showed the value of the use of pure yeasts in fresh fruit juice* 

 The following tests, with small amounts of apple juice sown with 

 pure yeasts in flasks of sterilized and unsterilized must, further illus- 

 trate this point. 



GROWTH OF YEAST IN STERILIZED AND UNSTERILIZED JUICE. 



Four flasks, each containing 400 cc of fresh juice, were used for 

 this test. No. 1 was left unsown as it came from the press. No. 2 

 was sown when fresh from the press with 1 cc of a vigorous culture 

 of yeast No. 8. Nos. 3 and 4 were quickly sterilized by holding at 

 steam heat for twenty minutes in a sterilizer, then rapidly pooled 

 under the water tap and sown with yeasts, as f ollows : No. 3 received 

 1 cc of yeast No. 8 and No. 4, 1 cc of yeast No. 66. These four flasks 

 were then put in the culture oven and kept at a temperature ranging 

 from 21 to 27 C. for a period of twenty-one days, at which time 

 the weights became nearly constant. The following tabular state- 

 ment shows the composition of the original juice and of each flask at 

 the close of the period. 



TABLE I. Composition of original must and of four flasks differently treated, 

 after a period of twenty-one fl<ni* (umili/xi* lit/ Hurra it of <'hrin\*try, U. 8. 

 Department of Agriculture). 



[Grams per 100 cc.] 



These results show clearly that yeast fermentation in flask No. 1 

 (unsown) was not properly developed. There remained 3.51 per 

 cent of total sugar when the weights became fairly constant. The 



