ALCOHOLIC FERMENTS. 145 



(/) The Behaviour of the Saccharomycetes and Similar 

 Fungi towards the Carbohydrates and other Constituents of 

 the Nutritive Liquid. Diseases in Beer. The first striking 

 proof of the fact that Saccharomyces species can perform 

 very different work in the nutritive liquid, was obtained after 

 Hansen's discoveries, by means of pure cultures of the yeasts 

 prepared in the Carlsberg laboratory, and afterwards in many 

 other laboratories, and which were subsequently tested in 

 practice. There are in fact breweries in which a large 

 number of different species of yeast have been tried on a 

 large scale and under the same conditions, and where the 

 attenuation, taste, odour, time of clarifying, and permanence 

 as regards yeast turbidity, &c., &c., have been found to differ 

 for each individual species. 



Hansen's epoch-making researches on the disease-yeasts 

 (1883) again showed, from another point of view, the marked 

 differences amongst the Saccharomyces species in their action 

 on the nutritive liquid ; he discovered, namely, groups of the 

 so-called wild yeasts, which bring about detrimental changes 

 in beer, whilst others were found to be harmless. Amongst 

 the former, again, there are some which communicate a bitter 

 taste and disagreeable odour to the beer (Sacch. Pastorianus 

 /.) without as a rule producing ^urbidity ; whilst others only 

 fully develop their activity in a late stage of the secondary 

 fermentation, and cause the beer to become turbid (Sacch. 

 Pastorianus III. and Sacch. ellipsoideus II.), in that an 

 abundant yeast deposit forms in a comparatively short time in 

 the finished beer after it has been drawn off. It is only when 

 these species Sacch. Pastorianus /., Sacch. Pastorianus 

 III., and Sacch. ellipsoideus II. are introduced into the 

 wort at the commencement of fermentation that they are 

 able to induce disease. The addition of disease-yeast to the 

 beer in the store casks or to the drawn-off beer has no 

 appreciable effect ; the inoculation of bottled beer with Sacch. 

 ellipsoideus II. will only take effect when the beer has been 

 very strongly infected. The main result is that the danger 



