THE CLARIFICATION OF FRUIT JUICES. 7 
preliminary pasteurization and sedimentation, with various amounts 
of each of the carbons, followed Hy the removal of the carbon and 
the subsequent examination of the juices with 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 débris 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 Marea (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 
earbon “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 
