APPLICATIONS OF FERMENTATIVE PEOCESSES 211 



the ascertainment of these favourable conditions. The production of 

 alcohol by yeast-fermentation has reached such a high pitch of excel- 

 lence that, when conducted on the most approved methods, failure is 

 almost impossible, in spite of the fact that wort is a suitable medium 

 for the growth of many bacteria and other small organisms. A list of 

 fermentative industries could be made, graded according to the scientific 

 knowledge of the processes involved. The bottom of this list would 

 include those fermentative processes which are entirely left to chance, 

 and in which even the organisms responsible for the fermentative 

 changes are unknown. With regard to the majority of such processes 

 the sum total of our knowledge is extremely small, though here and 

 there small additions are being constantly made. 



§2. THE PEODUCTION OF ALCOHOL. 



As already mentioned, this is the oldest fermentative industry of 

 which we have any knowledge. We learn from Herodotus that the 

 ancient Egyptians made wine from barley, and we are told by Pliny 

 that all the nations of Western Europe made beer. In some form or 

 other alcoholic beverages are partaken of, by almost every people on 

 the face of the earth. 



The methods adopted in such an excellent brewery as the Carlsberg 

 Brewery in Copenhagen represent the highest pitch of excellence that 

 any fermentative industry has yet achieved. In principle the produc- 

 tion of alcohol is simple. Into a sugary solution is introduced one or 

 other of the Yeasts. This is allowed to grow and multiply, the result 

 being the transformation of the sugar into alcohol. 



(a) Beer. In making beer, the brewer does not start directly from 

 sugar, but from starch, which can readily be converted into sugar. We 

 must therefore distinguish two phases : 



(i) The production of sugar from starch, 

 (ii) ,, alcohol from sugar. 



We have already explained how barley grains are converted into malt, 

 and have noted that the latter contains essentially starch and the 

 ferment diastase, which can change this starch into sugar. In the malt 

 condition, however, diastase is ineffective, owing to the absence of 

 moisture. The process of brewing may be divided into six stages : 



1. Grinding. The malt is bruised or crushed, and left in a heap for 

 a few days to allow it to mellow. This enables the diastase to be 

 more easily abstracted. 



