MICROBIOLOGY OF ALCOHOL AND ALCOHOLIC PRODUCTS. 419 



Fortified wines (sweet wines are usually fortified) contain 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 in- 

 sects. 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, Penicillium, 

 Dematium, Aspergilhts, 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 con- 

 stantly present in larger or smaller quantities. All these molds are harm- 

 ful to the grapes and the wine. Some of them, such as Penicillium, may 

 give a disagreeable, moldy taste to the wine, sufficient to spoil its com- 

 mercial value. Others, such as some Mucor s and Aspergilli may injure 

 the wine but slightly except by destroying the sugar and diminishing the 

 alcohol. Dematium pullulans may produce a slimy condition in weak 

 white musts and most of them may injure the brightness and flavor to 

 some extent. 



On sound ripe grapes these molds occur in comparatively small num- 

 bers 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, they may be 

 present in sufficient quantities to spoil the grapes before they are gathered. 

 On sound grapes which are gathered and handled carelessly, they may 

 develop sufficiently before fermentation to injure or spoil the wine. 



An exception to the generally harmful effect of these molds is Botrytis 

 cinerea (Sderotinia fuckeliana) which under certain circumstances may 

 have a beneficial action. When the conditions of temperature and mois- 

 ture are favorable, this mold will attack the skin of the grape, facilitating 

 evaporation of water from the pulp. This results in a concentration of 

 the juice. The mycelium then penetrates the pulp, consuming both sugar 

 and acid, principally the latter. The net result is an increase in the per- 

 centage of sugar and a decrease in that of acid. This, where grapes ripen 

 with difficulty, is an advantage, as no moldy flavor is produced. Two 

 harmful effects, however, follow: the growth of mold results in the 



