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BACTERIOLOGICAL METHODS 



pullulans, which shows septate branching hyphal filaments and 

 yeast-like sporulation, which might be mistaken for yeast cells. 

 h. Turning or Souring of Beer. — Soured, turned or spoiled 

 beers have a disagreeable taste and odor and are no longer clear or 

 brilliant and sedimentary deposits are usually found. Beers 



Fig. 75. — Saccharomyces cerevisece. The variety known as brewers' bottom 

 yeast (Unterhefe). a, Spore formation; b, elongated cells (rudimentary filaments 

 or hyphs). 



containing only a small amount of hops or of hop extract and 

 which are low in alcohol and inadequately filtered, pasteurized 

 and improperly bottled, are likely to spoil. The most common 

 cause of this kind of spoihng is due to the aerobic acetic acid 

 bacteria which are particularly apt to do great damage in the 

 top fermented beers where the conditions for their development 



