THE CLARIFICATION OF FRUIT JUICES. 3 



chemistry. It is known that the specific flavor of a fruit juice is 

 determined in part by the ratio borne by one of the colloids (tamiin) 

 to the acid and sugar content and in part by very imperfectly known 

 and complex constituents which are probably in the colloidal condi- 

 tion. While many of the pigments which give juices their color are 

 crystalline substances, others are either colloids or closely associated 

 with colloids. In order that a juice may be clarified without reducing 

 its value as a beverage, these constituents must remain unaltered by 

 the treatment, which must at the same time completely remove from 

 the liquid other colloids, including pectins, gums, complex carbo- 

 hydrates, and nitrogenous bodies. The methods which may be em- 

 ployed to make such a separation are greatly restricted by the condi- 

 tions, and the preservation of desirable constituents is more difficult 

 than the removal of the undesirable ones. This is especially the case 

 in devising methods which the small producer without special equip- 

 ment can use. 



For these reasons, the literature dealing, both from the theoretical 

 and from the practical point of view, with the clarification of such 

 colloidal solutions as are encountered in brewing, wine making, and 

 sugar manufacture was examined for suggestions as to possible lines 

 of attack, and considerable time was spent in determining the appli- 

 cability to the problem in hand of methods used in these industries. 

 No attempt to review this enormous literature will be made, but it 

 may be of interest to state the unsatisfactory or negative results ob- 

 tained in attempts to utilize some of these methods before describing 

 the method found most effective, 



METHODS OF CLARIFICATION GENERALLY EMPLOYED. 



The methods of clarification employed by wine makers and brewers 

 and in sugar manufacture may be grouped broadly into three classes : 



(1) Those in which the colloid is destroyed by the use of enzyms; 



(2) those which bring about by chemical treatment the formation 

 of a precipitate which " envelops " and carries down suspended ma- 

 terial; and (3) those in which the colloid is removed by adsorption 

 upon insoluble, chemically inert adsorbing agents. 



CLARIFICATION BY MEANS OF ENZYMS. 



The Wallerstein (10, £7, -28, 29) 1 process for the prevention of the 

 development of cloudiness, or " haze," in bottled beer when placed 

 upon ice prior to serving is an instance of the first treatment. Ac- 

 cording to the results of Brown's extended investigations (4), the ap- 

 pearance of " haze " under such conditions is due to the presence in 



1 Serial numbers (italic) in parentheses refer to " Literature cited " at the end of 

 this bulletin. 



