MICROBIOLOGY OF ALCOHOL AND ALCOHOLIC PRODUCTS. 429 



Such yeasts are being used extensively in Germany, France and Italy, usually with 

 excellent results. The methods of use would require too much space to describe here, 

 but they are simple and such as could easily be devised by anyone with some knowl- 

 edge of microbiological technic. They do not aim at obtaining an absolutely pure 

 fermentation, which is unnecessary, but endeavor to have an overwhelming proportion 

 of a thoroughly tested and suitable yeast which will rapidly and perfectly attenuate the 

 wine before the few injurious microorganisms present have time to do any harm. 



DURING FERMENTATION. However carefully the injurious germs 

 have been excluded and the good yeast increased, fermentation will not 

 be successful unless conditions as favorable to the latter and unfavorable 

 to the former as possible are maintained. 



The temperature of the crushed grapes or expressed must is of 

 importance. If it is below 15, unless the weather is warm, the grapes 

 should be warmed to 20 or 25. Unless this is done, the molds and 

 S. apiculatus, which require less heat than S. ellipsoideus will develop 

 more quickly. This is especially true when starters are not used. In 

 the warmer and earlier districts the grapes are practically never too 

 cold. On the other hand, unless there is great carelessness, the grapes 

 are never too warm for the commencement of fermentation. The 

 warmer they are, however, the more artificial cooling will be necessary 

 later, and the sooner it will have to be applied. 



Thorough crushing is necessary in the case of white wine, to facili- 

 tate the expression of the juice. For red wine, the grapes are also thor- 

 oughly crushed and the skin, pulp and juice are fermented together. 

 Imperfectly crushed grapes ferment unevenly and incompletely; the 

 growth of mold, is much facilitated. 



The must should be thoroughly saturated with air at the beginning 

 of fermentation to insure the multiplication of the yeast. The aeration 

 received in the processes of stemming, crushing and pressing is usually 

 sufficient for this purpose. More aeration would be harmful by in- 

 juring the flavor and color of the wine by over-oxidation and promoting 

 the growth of injurious aerobic organisms. An objection to the sterili- 

 zation of must by heat is the expulsion of the air and the difficulty of 

 replacing it in the proper amount. 



The proper use of sulphurous acid in the regulation of fermenta- 

 tion is one of the most important and necessary but least understood 

 parts of the wine-maker's art. Only by this proper use can wholesome 

 wine of the highest quality be produced. Improper use will injure 



