180 COLLOIDS IN BIOLOGY AND MEDICINE 



A perfect beer should be absolutely clear; turbid beers are unre- 

 liable, but no objection can be raised to a dusty or net-like appearance. 

 In the latter case the disperse phase consists of protein particles, dex- 

 trins or precipitates of hop resin. Some yeast may also be suspended. 



Occasionally in very cold beers cloudiness develops which may be 

 ascribed to precipitated albumins, which disappear when the beer is 

 warmed. In the United States where iced drinks are in great de- 

 mand, especial pains have been taken to master the difficulty. 



The alkalinity of the wash water, the carbonic acid, and the 

 atmospheric oxygen during the brew, play an important role in the 

 resistance of beer to cold. According to R. EMSLANDER* the surest 

 means is the addition of some pepsin. [Wallerstein has patented 

 the addition of a proteolytic enzyme to beers, to prevent cold- 

 cloudiness. Tr.] 



What is designated as "vollmundigkeit" or body in beer is caused 

 by the colloid content. This property is almost identical with the 

 viscosity, and is determined by the viscosimeter. If, for instance, the 

 time required for water to run from a 50-c.c pipette = 1, and that of 

 an equal quantity of beer = 1.43, we say that the "viscosity" is 1.43. 

 It follows from what has been said on pages 152 and 153, that we 

 may assume a priori, that the "vollmundigkeit" is largely dependent 

 on the electrolytes, that is, on the content of acids and the kinds of salts. 

 Even though the larger part of the salts is derived from barley, yet 

 some are derived from the brewing water, and the hitherto partly 

 unrecognized influence of the water may be attributed to this fact. 



E. MOUFANG determined empirically the relation between optimum 

 keeping quality, "full" and " palatable" taste, sediment and acidity. 

 I refer to F. EMSLANDER * J for the colloid-chemical effect of the 

 brewing water on lagered beer. 



Among the proteins, in addition to the gluten which flocculates out 

 on boiling with acetic acid, peptone may be mentioned. H. BECH- 

 HOLD * 8 was able to demonstrate only albumoses, upon examining a 

 beer by ultrafiltration. Before generalizing, a large number of beers 

 would have to be investigated in this way. It seems that E. FOUARD 

 has carried on such ultrafiltration experiments with starch solutions, 

 worts and beer (cited by EMSLANDER). W. H. VAN LAER has also 

 made noteworthy experiments on the relationship between the ultra- 

 filtrates of beer and musts, and their transparency. F. EMSLANDER 

 and H. FREUNDLICH * have performed cataphoretic experiments and 

 found that the colloids migrate to the cathode. In consideration of 

 the acid content of beer, this finding is theoretically correct. 



R. MARC* has worked out a simple method for quantitatively 

 determining beer colloids by means of the fluid interferometer. 



