DIVISION VI 



MICROBIOLOGY OF ALCOHOLIC FERMENTATION AND 



DERIVED PRODUCTS* 



CHAPTER I 



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 

 made from both the juice and skins of red grapes. 



Wine in the proper sense is therefore produced exclusively from 

 fresh grapes. Much so-called wine is made in many countries from 

 dried grapes or mixtures of grapes and other fruits with sugary materials 

 of various kinds and various coloring and flavoring substances. Some 

 contain no grapes at all. In most countries, these beverages cannot 

 be sold without some qualifying designation, such as modified, amelio- 

 rated, or imitation wine, or piquette, plum wine, gooseberry wine, etc. 



GRAPE JUICE 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 



* Prepared by F. T. Bioletti. 



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