12 BULLETIN 1025, U. S. DEPARTMENT OF AGRICULTURE. 



loganberry (Logan blackberry) juices, adding that it may affect 

 flavor. As this author states elsewhere in the same publication that 

 egg albumen, casein, and Spanish clay are the clarifying agents 

 which have been found most satisfactory for use with fruit juices in 

 his laboratory, he evidently did not consider that diatomaceous earth 

 had possibilities for the purpose. 



Wilson (32) in a very recent paper outlining the method of manu- 

 facture of citric acid from lemons, states that prepared diatomaceous 

 earth is added to the raw juice, the liquid then being heated to boil- 

 ing and passed hot through the filter press, which is said to deliver 

 " a brilliant amber-colored juice." 



EXPERIMENTS WITH DIATOMACEOUS EARTH FOR CLARIFYING 



FRUIT JUICES. 



The writer's experimental work with diatomaceous earth was 

 begun in the autumn of 1918, prior to the publication of the group of 

 recent papers just cited and without knowledge of the work under 

 way in the various laboratories from which they came. It was sug- 

 gested, however, by such references to the use of diatomaceous earth 

 in the clarification of cane juices as are found in the older standard 

 handbooks on sugar manufacture. The possibilities of a material 

 combining insolubility, a high degree of freedom from contaminat- 

 ing foreign matter, and immense absorbing surface were immediately 

 obvious, and various samples of diatomaceous earth, of both Ameri- 

 can and foreign origin, were obtained for use in preliminary experi- 

 ments. In these tests a relatively small number of apple and grape 

 juices, selected so that they might fairly represent the range of 

 variation in color and in physical characters found in these juices, 

 were employed. All the tests in 1918 were made upon juices previ- 

 ously pasteurized and stored until sedimentation had ceased, but all 

 were opaque, turbid solutions. 



It was immediately apparent that diatomaceous earth combined 

 excellent clarifying power with very slight or insignificant effect 

 upon the coloring matter of apple and grape juices. In every case 

 the effect of treatment with the earth was an apparent deepening 

 of the color of the liquid due to its transparency after removal of the 

 colloidal material, so that visitors to the laboratory refused to believe 

 that treated juices had not been artificially colored. There was 

 noticeable in all the more delicately flavored juices a peculiar altera- 

 tion in taste, described by some as an " earthy " flavor, by others as 

 a " rancid, old-butterlike " taste. This was more marked in samples 

 treated with one of the lots of diatomaceous earth than in others but 

 was perceptible in all. It was attributed to the presence of a soluble 

 impurity in the earth. The fact that living diatoms contain amounts 



