THE MICROBIOLOGY OF ALCOHOL PRODUCTS 

 Composition of Must and Dry Wine 



507 



Fortified wines (sweet wines are usually fortified) usually con- 

 tain enough alcohol to make them practically antiseptic to all 

 microorganisms. 



The Microorganisms Found on Grapes 



On the surfaces of grapes, as they are brought to the cellar, may be 

 found any of the bacteria and fungi usually carried by the air and by 

 insects. Many of these are incapable of growing in grape must, and 

 are, therefore, without effect on the wine. 



Molds. — ^The spores of the common saprophytic molds, Penicil- 

 lium, Dematium, Aspergillus, Mucor, are always present in abundance, 

 and they find in must excellent conditions for development. Botrytis 

 cinerea, a facultative parasite of the leaves and fruit of the vine, is also 

 nearly always present in larger or smaller quantities. All these molds 

 are harmful to the grapes and the wine. Some of them, such as Penicil- 

 lium, may give a disagreeable, moldy taste to the wine, sufficient to 

 spoil its commercial value. Others, such as some Mucor s and Asper- 

 gilU may injure the wine but slightly except by destroying sugar and 

 diminishing the alcohol. Dematium pullulans may produce a slimy 

 condition in weak white musts and most of them may injure the 

 brightness a/nd flavor to some extent. 



On sound ripe grapes these molds occur in comparatively small 

 numbers and being in the spore or dormant condition they are unable 

 to develop sufficiently to injure the wine under the conditions of proper ' 

 wine making. On grapes which are injured by diseases, rain or insects, , 



