FOODS AND CONDIMENTS 181 



A study should be made of the usefulness of several other colloid- 

 chemical methods for the testing of beer, especially the determina- 

 tion of surface tension, which might serve to distinguish the amount 

 of various colloids contained, coagulation methods, etc. The mere 

 suggestion should suffice. 



It must be mentioned in addition, that F. EMSLANDER* 2 has at- 

 tributed to the "protective colloids" of beer a significance for the 

 more easy adsorption of milk and other foodstuffs. Even earlier 

 experiments, especially those of Ross VAN LENNEP indicate that the 

 presence of colloids and suspensions have an influence on the growth 

 of microorganisms. S"HNGEN thoroughly investigated this matter 

 in connection with alcoholic fermentation and obtained interesting 

 results. He found that colloidal iron, albumin, silicic oxid and 

 humic acid had no influence on alcoholic fermentation, but that, on 

 the contrary, it was greatly hastened by turf, filter paper, blood 

 charcoal and garden earth. He succeeded in proving the cause of 

 this; the carbonic acid which is developed during alcoholic fermen- 

 tation impedes fermentation and all substances which favor the dis- 

 appearance of the carbonic acid favor fermentation. The action of 

 the colloids mentioned is purely mechanical, somewhat like that of 

 powdered glass, threads, wood chips or platinum shavings which 

 hinder boiling. In the fermentation industry it is generally known 

 that brewers grains and spun glass increase alcoholic fermentation, 

 and these phenomena have now been explained by SOHNGEN'S 

 investigation. 



S. ROTHENFUSSER * has employed his colloid-adsorption method 

 for detecting saccharose in the most diverse kinds of foods and condi- 

 ments (wine, weissbier, cafe* parfait, kilned malt, pastry, etc.). 



In practice naturally many other questions will appeal to food 

 chemists. It might be determined whether the availability of vege- 

 table protein, which on digestion is only from 60 to 70 per cent, 

 could not be increased by a suitable method of preparation. Colloid- 

 chemical methods must unquestionably be utilized in the investiga- 

 tion of fruit juices, jellies and marmalades. We must remember that 

 these are frequently mixed with glucose, which, when undeclared, 

 should be regarded as an adulteration. Glucose contains in addition 

 to dextrose, dextrin and unfermentable substances which may be 

 determined by colloid-chemical analysis. Marmalades are adulter- 

 ated with gelatin^ agar-agar and isinglass. 



We trust that the mere mention of these facts may cause food 

 chemists to give greater attention to colloid-chemical methods. 



