i84 CHEMISTRY OF THE YEAST CELL. 



by the researches of A. Reichard (III.). One of the physio- 

 logical causes determining the appearance of this undesirable 

 phenomenon will be found mentioned in § 258. 



Furthermore, only a few words can here be devoted to the 

 so-called frothy fermentation which occurs in spirit distilleries, 

 because the causes of this phenomenon have not yet been 

 sufficiently investigated to furnish results that could be dealt 

 with in the limits of the present woi'k, or permit any reli- 

 able conclusions to be drawn. Nevertheless, all the observa- 

 tions on this point recorded in practice may be mentioned as 

 affording noteworthy hints for the more accurate examination 

 of the matter by fermentation physiologists. Special attention 

 may be di-awn to the observations recorded by M. Delbrueck 

 (I.). In the normal course of fermentation in potato distilleries, 

 the upper layers of head formed on the surface of the mash 

 disappear in proportion as fresh portions are thrown up from 

 below ; whereas, when frothy fermentation occurs, the upper 

 bubbles do not burst, but the thickness of the head goes on 

 increasing, until the entire contents of the vat seem to be in a 

 state of ebullition, and thick masses of froth overflow the top 

 of the vessel. This is a direct source of loss, the more so in 

 countries where the excise regulations prohibit the recovery of 

 the overflow. In many cases the evil may be either entirely 

 remedied, or reduced to a minimumj by pouring a little oil into 

 the contents of the vat as soon as frothy fermentation becomes 

 manifest. Yeasts of high fermentative power are especially 

 liable to this evil, ejj. the so-called Race II. already mentioned 

 (page 112); though in other respects this is a very useful yeast. 

 A few observations on this point have been communicated by 

 M. BuECHELER (I.), and further information thereon is con- 

 tained in M. M^rcker's handbook on the manufacture of spirits 

 (I.). Undoubtedly the occurrence of frothy fermentation is 

 determined by special physiological conditions, based on the 

 method of nutrition of the yeast : for example — according to 

 R. KussEROW (I.) — the simultaneous presence of large amounts 

 of amides and peptones in the nutrient svibstratum. This has 

 been borne in mind in arranging a modification of the mashing 

 process in cases where there is a possibility of this frothy 

 fermentation being set up. According to the method proposed 

 by Hesse, a distillery manager, of Wutzig — as reported by M. 

 Delbrueck (II.) — only one-half of the malt requisite for the 

 saccharification process is introduced into the warm mash, the 

 remainder being added after cooling and the introduction of the 

 pitching yeast. The results of this ti'eatment are reported by 

 G. Heinzelmann (I.) to be satisfactory, almost without ex- 

 ception. In pressed yeast works it also occasionally happens 

 that riotous fermentation is set up in the vats. With regard 

 to the incorrectly named frothy fermentation occasionally met 



