254 INTERNATIONAL CONGRESS OF VITICULTURE 



SOME EESULTS OF THE PRACTICAL APPLICATION OF 



SULFUROUS ACID AND SELECTED YEAST IN THE 



FERMENTATION OF CALIFORNIA "WINES, 



1913 AND 1914. 



By W. V. CRUESS, 



Division of Viticulture, University of California. 



Most published data on the effect of sulfurous acid and pure yeast on 

 the quality of wines deal with figures obtained under carefully controlled 

 experimental conditions; very little information is available on the results 

 obtained from their use by practical wine makers. For this reason the com- 

 position of wines from California cellars using sulfurous acid and pure yeast 

 in fermentation has been compared with the composition of wines made in the 

 same localities by the old method of "natural" fermentation. The analyses 

 represent thirty-three different cellars and for that reason can probably be 

 taken as being more or less representative of California conditions. 



The methods in which the pure yeast and sulfurous acid were applied by 

 the wine makers in the manufacture of the wines discussed in this paper may 

 be described briefly as follows: 



A quart bottle containing pure "Burgundy"! wine yeast growing on agar 

 must is sent by the Enology Laboratory to the wine maker applying for it. 

 He fills the flask with sterile must. When this is in vigorous fermentation, 

 it is used to inoculate two gallons of sterile must, and this, when in fermenta- 

 tion, is poured into 25-50 gallons of must, either sterilized previously by 

 heating with steam, or previously treated with a small amount of sulfurous 

 acid, settled and racked before adding the yeast. The larger lot of inoculated 

 must is aerated and kept warm artificially till in active enough fermentation 

 to be used to inoculate a tank of crushed grapes or white must. 



The first tank of crushed grapes is treated at or immediately after crush- 

 ing with 8-12 oz. potassium metabisulfite (K 2 S 2 O 5 ) per ton. This amounts to 

 approximately 275-412 milligrams metabisulfite per kilo or 137 to 206 mgms. 

 SO 2 per kilo, figuring K 2 S 2 O 5 at 50% SO 2 . The sulfited grapes are allowed 

 to stand a few hours (2-4) after crushing. The vat is then inoculated with 

 the 25-50 gallons of yeast. When in fermentation, a portion of this vat is 

 used to start the next vat of crushed and sulfited grapes. This process is 

 repeated successively through the season. This is practically the method 

 advised in Circular 119 of the University of California Station.2 



Some of the more careful wine makers maintain a pure yeast apparatus 

 from which each vat is inoculated. The method followed consists in replac- 

 ing the liquid used from the first 50 gallons of yeast for inoculation by must 

 previously treated with metabisulfite and cleared by settling 24 hours. 



iThe "Burgundy" yeast was sent the station several years ago by the 

 Ecole National d' Agriculture at Grignon, France. It has a high fermenting 

 power and settles rapidly after fermentation. 



^Circular 119, University of California Station, "Winery Directions," by 

 Professor F. T. Bioletti. 



