FJERMENTATION 257 



CeHiA = 2C,H,OH + 2C02. 



Glucose. Alcohol. Carbonic 

 acid gas. 



When the proportion of alcohol produced in a fermenting 

 liquid amounts to 12 per cent., the further growth of the 

 yeast is prevented, and with 14 per cent, fermentation 

 ceases altogether. Temperature, again, is a most important 

 factor in alcoholic fermentation, 25° to 30° C. being on the 

 whole most favourable. 



Hansen, of Copenhagen, has enormously extended our 

 knowledge of the yeasts. He has shown that there are a 

 number of distinct forms, differing, it is true, but little 

 among themselves in shape, but possessing very distinct 

 properties, more especially in respect of the nature of 

 certain small quantities of secondary products to which they 

 give rise, which are highly important as giving character to 

 the beers produced. Hansen has shown how these varieties 

 of yeast may be grown or cultivated in a state of purity 

 even on the industrial scale, and has in this manner 

 revolutionised the practice of brewing, particularly on the 

 Continent. During recent years these pure yeasts, each 

 endowed with its particular properties, have been grown 

 with scrupulous care in laboratories equipped especially for 

 the purpose, the pure growths then being despatched to 

 different parts of the world, particular yeasts being 

 employed for different beers. In this way scientific 

 accmracy and the certainty of success are introduced into 

 an industry in which much was left to chance, and in 

 which everything was subordinated to tradition and 

 empiricism. 



Hansen carried on his researches on a most extensive 

 scale in connection with the large brewing industry at Old 

 Carlsberg in Copenhagen, where very naturally he gave 

 early attention to the study of the saccharomycetes. 



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