tHAPTER VII* 

 THE MICROBIOLOGY OF ALCOHOL PRODUCTS 



Wine 



Wine may be defined shortly as the product of the alcoholic fer- 

 mentation of sound, ripe grapes and the usual cellar treatment. 



The classifications of wines are numerous and the varieties in- 

 numerable. They may be separated, however, into a few main groups, 

 depending on chemical composition and methods of manufacture. 

 Dry wines are those in which practically all the sugar has been re- 

 moved by fermentation; sweet wines, those in which enough sugar 

 remains or is added to, be noticeable to the taste; fortified wines, those 

 that have received an addition of distilled wine spirits; and sparkling 

 wines, those highly charged with carbon dioxide, produced by supple- 

 mentary fermentation in the bottle. Each of these groups includes 

 white wines made from the expressed juice of the grape, and red wines 

 matde from both the juice and skins of red grapes. 



Grape JincE and Wine as Culture Media 



Grape juice, known technically as must, is a sugary, acid, organic so- 

 lution very favorable to the growth of yeasts and of many other fungi, 

 but unfavorable to most bacteria. Wine is of a similar composition but 

 contains alcohol instead of sugar and is, therefore; less favorable to the 

 growth of most microorganisms. Both liquids are of highly complex 

 composition. Their character as culture media is indicated by the 

 following table: 



• Prepared by F. T. Bioletti. 



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