424 



MICROBIOLOGY OF SPECIAL INDUSTRIES. 



Much larger amounts are injurious in two ways. When the acetic 

 acid is perceptible to the taste, the wine is spoiled. When an abnormal 

 amount of acetic acid is produced before or during fermentation it 

 interferes with or stops the work of the yeast. In such cases, the wine 

 "sticks," that is, fails to eliminate all its sugar and becomes especially 

 liable to the attacks of other bacteria. 



Wines high in alcohol are less liable to acetic fermentation than weaker 

 wines. Sound wines containing over 14 per cent by volume of alcohol 

 are almost immune, but such wines may be spoiled during fermentation 

 by the growth of acetic bacteria on the exposed floating "cap" of pomace 

 or on the crushed grapes, especially at high temperatures. 



ANAEROBIC ORGANISMS (Facultative and Obligate). Some of the 

 worst, most frequent, and most difficult to treat diseases and defects of 

 wine are due to organisms which develop only in the absence of oxygen. 

 These organisms are all bacteria and appear to include a large number 

 of forms, though, owing to difficulties of isolation and culture, the di- 

 ferent forms have not been well studied or described. 



'*!>. < 



FIG. 86. Bacteria of slimy wine. A, B,C, pure cultures of various forms; D, muci- 

 laginous sheath of slime bacteria. (After Kayser and Manceau.') 



Slime-forming Bacteria. Musts and wines become slimy rarely 

 through the action of Dematium pullulans (Wortmahn) and wild yeast 

 (Meisner) in the presence of oxygen but more frequently through the 

 action of bacteria. In most cases only young wines after fermentation 

 and when contained in closed casks or bottles exhibit this defect. A 

 slimy wine has an oily appearance, pours without splashing and in 

 extreme cases, becomes cloudy and will hang from a glass rod in strings. 



In such wines, the microscope reveals large numbers of almost 

 spherical or more or less elongated bacteria in long chains. Other ob- 



