ALCOHOLIC FERMENTS. 171 



whilst the Carlsberg beers gave the following numbers : 



Alcohol. Glycerine. 



No. 1, 100 2-63 



No. 2, 100 3-24 



It is thus seen that, as BORGMANN suggests, good beer may 

 be produced in which the ratio of glycerine to alcohol is lower 

 than the previously admitted minimum. 



A series of eight different species of Saccharomyces, and 

 amongst them six " cultivated " yeasts, all in absolutely pure 

 cultures, were examined by AMTHOR with reference to their 

 chemical action on beer-wort. His results again confirmed 

 HANSEN'S principle, that, in practice, a careful selection must 

 always be made. The fermentations were conducted in 

 Pasteur flasks of one litre capacity under identical condi- 

 tions, and in two series, the first of which corresponded to 

 the primary fermentation in the brewery, and the second 

 series to the secondary fermentation. The alcohol, extract, 

 specific gravity, attenuation, glycerine, nitrogen, reducing sub- 

 stance and the degree of colour, were determined in the 

 fermented worts. The tables show palpable differences in the 

 work accomplished by the different species. The percentage 

 of alcohol (by volume) varied within the limits 4*34 and 6 '02 

 (3 '5 5 to 5 '9 4 at the end of the primary fermentation), the 

 extract from 8'27 to 11-23 (8'49 to 12-61 at end of primary 

 fermentation), the attenuation from 36'7 to 53*3 (28*8 to 

 52'1 at end of primary fermentation) ; the percentage of 

 glycerine showed very striking differences and fluctuated 

 between 0'08 and 0'15 ; and likewise the amounts of nitrogen 

 and reducing substance, and to some extent even the degree of 

 colour, showed considerable differences. 



HIEPE drew some interesting parallels between the be- 

 haviour of a number of culture yeasts and wild yeasts towards 

 the sugars. For this purpose he instituted fermentations in 

 cane sugar solutions to which yeast water had been added. 

 He took out the first sample five minutes after the fermenta- 

 tion had been induced, and then fresh samples every day, 

 till the fermentation had subsided. In each sample the 

 amount of (1) inverted cane-sugar, (2) fermented extract, (3) 

 fermented dextrose, and (4) fermented Isevulose, was determined. 



