SIO MICROBIOLOGY OF SPECIAL INDUSTRIES 



materials of the must and when allowed to develop cause cloudiness 

 and various defects in the wine. 



The most important and abundant is the apiculate yeast, S. api- 

 culatus. According to Lindner this is a true yeast, producing endo- 

 spores. The cells of this organism are much smaller than those of 

 S. ellipsoideus and very distinct in form. In pure culture these cells 

 show various forms, ranging from ellipsoidal' to pear-shaped (apiculate 

 at one end) and lemon-shaped (apiculate at both ends). These forms 

 represent simply stages of development. The apiculations are the 

 first stage in the formation of daughter cells, the ellipsoidal cells, the 

 newly separated daughter cells, which later produce apiculations and 

 new cells in turn. 



Many varieties of this yeast occur, as in the case of S. ellipsoideus. 

 They are widely distributed in nature, occurring on most fruits, and 

 are particularly abundant on acid fruits such as grapes. Apiculate 

 yeast appears on the partially ripe. grapes before the true wine yeast 

 and even on ripe grapes is more abundant than the latter. The rate 

 of multiplication of this yeast is very rapid under favoring conditions 

 and much exceeds that of wine yeast. The first part of the fermenta- 

 tion, especially at the beginning of the vintage and with acid grape's, 

 is, therefore, often almost entirely the work of the apiculate yeast. 



The amount of alcohol produced by this yeast is about 4 per cent, 

 varying with the variety from 2 to 6 per cent. When the fermentation 

 has produced this amount of alcohol the activity of the yeast slackens 

 and finally stops, allowing the more resistant ellipsoideus to multiply 

 and finish the destruction of the sugar. The growth of 5. apiculatus, 

 however, has a deterring effect on that of the true wine yeast so that 

 where much of the former has been present during the first stages of 

 fermentation the latter often fails to eliminate all the sugar during the 

 last stages. 



When the apiculate yeast has had a large part in the fermentation, 

 the wines are apt to retain some unfermented sugar and are open 

 to the attacks of disease-producing organisms. Their taste and color 

 are defective, often suggestive of cider, and they are difficult to clarify. 

 This yeast attacks the fixed acids of the must, the amount of which is, 

 therefore, diminished in the wine, while on the other hand the volatile 

 acids are increased. • 



Many other yeast-Uke organisms may occur on grapes, but, under 



