YEASTS AND MOLDS 



33 



There are numerous varieties of Saccharomyces concerned in beer 

 brewing. There are several kinds of upper or top yeasts (Kahmhefe 

 Oberhefe) and several kinds of bottom or lower yeasts (Unterhefe), each 

 kind possessing supposedly special properties. Just what part the more 

 or less incidentally associated organisms (as bacteria, molds, and foreign 



PIG. 76. Sak6 making. Steamed rice cells (c) attacked by the hyphas (a) of 

 Aspergillus oryzce which feed upon the dex'.rinized rice starch, converting it into sac- 

 charine substances. Yeast cells and bacilli are usually associated with the hyphal fun- 

 gus, feeding upon the saccharine substances formed. 



yeasts) may play in the fermentation processes is not clearly understood. 

 It is known that some of these extraneous organisms may develop to such 

 an extent as to modify the quality of the product completely. Such fer- 

 mentation diseases are a source of much annoyance to manufacturers, 

 often resulting in great financial loss, but this has also been the great 

 stimulus in compelling the use of pure cultures and in perfecting those 

 methods which are known to improve the keeping qualities of the articles, 



