WHITE BEER, LAMB1C, GINGER-BEER. 255 



and a small quantity of volatile acids (acetic and formic acids), the 

 proportions varying with the kind of sugar and the conditions of 

 cultivation. Given a sufficiency of sugar, the degree of acidity 

 produced is then solely dependent on the composition of the 

 remainder of the medium ; in unhopped wort it amounts to as 

 much as 1.26 gram (calculated to lactic acid) per 100 c.c., whilst 

 in hopped wort it does not exceed 0.27 gram. The development 

 of the bacillus is not restricted by alcohol unless more than 7 per 

 cent, of this substance is present in the beer. It thrives better in 

 the warm, and consequently the malady is of frequent occurrence 

 in summer in countries where the cellar accommodation is defec- 

 tive. This explains the Flemish name "Zomerbier," applied to 

 turned beer in general. The organism cannot survive continuous 

 exposure to 55-6o C. for a short time; consequently beer in- 

 tended for export to tropical countries may be protected against 

 risk of " turning " by Pasteurisation. 



153. White Beer, Lambie, Ginger-Beer. 



A low percentage of lactic acid is met with even in the best 

 beers. It is derived partly from the malt itself, which contains 

 on an average 0.05 per cent, of this acid, but is chiefly produced 

 during the mashing process, the amount then developed being 

 nevertheless small ranging in normal beers between 0.05 and 0.2 

 per cent. The nature and amount of the acids produced during 

 the malting of barley, the kilning and mashing of the malt, and 

 the boiling of the beer-wort, have been investigated by E. PRIOR (I.). 

 In addition to the rod-shaped species already described, lactic fer- 

 ments, in the form of globular cells developing into sheet colonies, 

 appear in the malt-mash. An acid-producing species of this class 

 was examined by P. LINDNER (I.), who named it Pediococcus acidi 

 lactici. Its diameter is 0.6-1.0 p, and the optimum temperature 

 is about 40 C., but the organism is killed in two minutes by a 

 temperature of 62 C., and it does not thrive either in hopped wort 

 or beer. The spontaneous lactic fermentation appearing under 

 certain circumstances in malt-mashes has been investigated, from 

 a chemical point of view, by M. HAYDUCK (II.). The variety of 

 the fission fungi developing in these mashes is very considerable, 

 the first in point of size being the Sarcina maxima, described by 

 P. LINDNER (II.), the individual cells of the packet-colonies of 

 this organism measuring 3-4 ju, in diameter. Attempts to obtain 

 pure cultures of this, the largest species of sarcina, have hitherto 

 proved unsuccessful. 



In many instances the appearance of a vigorous lactic fermen- 

 tation in beer-wort is regarded with favour and its development 

 encouraged. This applies to the so-called "Weissbier" (white 

 beer). No careful bacteriological investigation of the acidification 

 process, which plays such an important part in the preparation of 



