TORULA. 391 



of these forms must be regarded as disease organisms, for 

 they immediately form a dry film, which afterwards, on shaking, 

 renders the beer turbid. In Danish, Swedish, and American 

 beers these species can also be detected. The conditions, 

 however, are extremely unfavourable for their development ; 

 this is especially the case with the low temperatures used in 

 the preparation of lager beer. According to Schionning, if 

 pure cultures of these forms are introduced into Continental 

 beers, they appear as true disease forms, imparting an un- 

 pleasant taste and smell to the beer. 



We are indebted to Will for one of the most complete 

 investigations of Torulas. His very comprehensive experi- 

 ments concern themselves, on the one hand, with a morpho- 

 logical description of the species during their cultivation on 

 different liquid and solid substrata, and with observations on 

 the influence of temperature (temperature limits for growth 

 of cells and influence on their shape). On the other hand, 

 he observed the behaviour of the species in competition 

 with different wild culture yeasts ; their reactions with the 

 sugars ; their power of forming glycogen in different liquids ; 

 their production of acid, and their power of producing sulphur- 

 etted hydrogen. 



He mentions fourteen different species derived partly 

 from air and water analyses, and partly from the laboratory. 

 Some are found in beer and some on grapes. They all 

 develop freely in hopped wort, even at low temperatures 

 such as may be used in the primary fermentation. They 

 develop distinct differences in flavour and aroma, the latter 

 often aromatic, but in some cases unpleasant. A slight 

 decolorisation of the wort takes place. The acidity is dim- 

 inished in the majority of cases, but increases with certain 

 species. The majority are suppressed when brought into 

 competition with different low-fermentation culture yeasts, 

 even when large amounts are used for inoculating, and this 

 takes place in the primary fermentation. Nevertheless all 

 the species do not behave alike in this respect, and again the 

 various races of culture yeasts are unequal in their power of 

 suppressing the Torulas. The Torulas have no influence on 

 the taste and odour of lager beer, and they do not bring 



