THE CLARIFICATION OF FRUIT JUICES. 7 



preliminary pasteurization and sedimentation, with various amounts 

 of each of the carbons, folloAved by the removal of the carbon and 

 the subsequent examination of the juices Avith respect to alteration 

 of color and flavor, degree of removal of colloidal matter, and 

 ability to withstand subsequent pasteurization without formation of 

 precipitate. In view of the character of the results, a detailed state- 

 ment of the experimental work is considered unnecessary, but a some- 

 what extended statement of the difficulties encountered may be made. 



(1) In order to produce anything approaching a satisfactory subsidence of 

 the precipitate after adding carbon it is necessary first to filter the juice, as 

 Gore (14) has pointed out. The filtration of freshly pressed apple or grape juices 

 by any of the ordinary methods is practically impossible, and even under 

 high pressure is extremely slow and difficult, as the filter quickly becomes 

 clogged with cellular debris and gummy material. The use of diatomaceous 

 ("infusorial") earth, which Gore has suggested as an aid to this preliminary 

 filtration, increases the rate somewhat, but does not eliminate entirely the 

 clogging and frequent stoppage of filters of any of the usual types. With grape 

 juice expressed after heating the fruit, it is a practical impossibility to make 

 such filtration. 



(2) The most marked property of all the carbons examined in the course of 

 the work was their high decolorizing power for both apple and grape juices. 

 While the samples differed markedly in this respect, the outstanding effect of 

 carbon treatment was in every case a very considerable lightening of color. In 

 very heavily pigmented red or purple grape juices this effect is not highly 

 objectionable, but in juices made from white or light-red grapes and in apple 

 juices the use of carbon produces very light straw-colored liquids, quite unrecog- 

 nizable as to source. Since the available carbons of vegetable origin had been 

 subjected to special treatments specifically designed to increase decolorizing 

 power, as Zerban (34) has pointed out, this result was to be anticipated in so 

 far as such special carbons are concerned, but the effect of boneblack upon the 

 color of the lighter juices was also so pronounced as to make its use inadvisable 

 except with very deeply colored juices. 



(3) All the carbons employed have a perceptible effect upon flavor. In the 

 case of some highly flavored, strongly foxy or musky juices, this effect, while 

 perceptible, is not undesirable, but in delicately flavored grape juices and in 

 apple juices it detracts materially from the beverage quality of the product. The 

 alteration is due in most part to the adsorption of tannin and in less degree to the 

 removal of acids by the carbon, as is shown by the decided improvement in flavor 

 produced by restoring these constituents in amounts equal to those removed. 

 But other unknown constituents which play a part in determining the character- 

 istic flavors of the several juices are also removed. This is shown by the fact 

 that juices " reconstituted " by additions of acid and tannin are always readily 

 distinguished by taste even by inexperienced persons from untreated samples 

 of the same variety. Treatment of the carbon prior to use by washing with a 

 dilute solution of tannic acid in malic or tartaric acid reduced the effect in so 

 far as these constituents are concerned, but it did not prevent perceptible altera- 

 tions in flavor. La Marca (16) in his work upon the clarification of wines, 

 found that the use of carbon reduced acidity, tannin content, and extractives, 

 and Gore (14) has stated that when orange or lemon juices are treated with 

 carbon " it is advantageous to add orange or lemon flavor, in the respective 

 cases, to the respective juices prior to sterilization, in order to restore their 



