PRODUCED BY ALCOHOLIC FERMENTS. 197 



infection of the bottled lager beer is without effect ; even in the 

 case of Sacch. ellipsoideus II. the beer must be comparatively 

 strongly infected before any effect is produced. What has been 

 said with regard to the infection of lager beer in bottles will, 

 in the main, also apply to the same beer in the small carnage 

 casks. 



Faultless beer, which has been fermented with a pure 

 culture of a good brewery yeast, will also form a yeast 

 sediment after it has remained a sufficient length of time 

 in the bottles and casks. As has already been shown, how- 

 ever, such a sediment is much slower in forming than a 

 disease yeast sediment. As a rule, I also found that there 

 was a distinct difference in the character of the sediment. 

 When the good beer was shaken it did not become cloudy ; 

 the yeast collected in small conglomerations, and these rapidly 

 settled again to the bottom. The yeast in the sick beer, on 

 the other hand, was loose, and rose as a cloud of cells when 

 the beer was slightly agitated, and when vigorously shaken 

 the beer became muddy. 



In none of the numerous experiments with the two yeasts 

 did I notice that they imparted any disagreeable taste or 

 odour to the beer, not even in cases where they had produced 

 pronounced yeast turbidity. A difference was detected by 

 experienced tasters, but was not recognisable as a disease. 



Before concluding this chapter, some observations relating 

 to one of the disease yeasts, namely, Sacch. Pastorianus III., 

 may here be mentioned. In one of my earlier researches I 

 briefly alluded to some observations I had made, with regard 

 to the importance of aeration of the wort. By cultivating 

 the Car Is berg bottom yeasts No I and No 2 separately in 

 aerated wort, I obtained pitching yeast which, under brewery 

 conditions, was normal in its clarifying properties. On the 

 other hand, when the same yeasts were grown in perfectly 

 similar wort, but which had not been aerated, I obtained 

 yeast which only behaved normally after it had gone through 



