BULLETIN No. 1025 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington, D.C. PROFESSIONAL PAPER January 23, 1922 
STUDIES IN THE CLARIFICATION OF UNFER- 
MENTED FRUIT JUICES. 
By JosepH S. CALDWELL, Plant Physiologist, Office of Horticultural and 
' Pomological Investigations. 
CONTENTS. 
Page. Page. 
Purpose and scope of the investiga- 
Experiments with diatomaceous earth 
eststh ee. DEE A REE Cera kt hg 1 for.clarifying fruit juices2_2__— — 12 
Methods of clarification generally Purification of the earth______ a 
TELS Up 2 fees se ae a lglg 3 Difficulties encountered in filter- 
Clarification by means of ing treated juices__________ 14 
Dit e 3 | Simple and effective methods of fil- 
Clarification by the formation tration with diatomaceous earth_ 1155 
DE PA DECCIN Mates ee ey et) 5 | Pasteurizing before filtering_______ 20 
Clarification by the use of inert Filtration of freshly pressed juices_ 20 
adsorbing agents___________ Ga lsumimanyeeet ee ee wer ae is S 26 
TiteracUTen Cube dies sy tk Se ys eh 28 
PURPOSE AND SCOPE OF THE INVESTIGATION. 
When an unfermented fruit j ice, such as that of apples or grapes, 
is prepared and preserved by the methods ordinarily employed, a_ 
more or less copious precipitate consisting of cellular débris and 
heat-coagulable material is formed after pasteurization. This fact 
is responsible for the usual practice of pasteurization and storage, 
followed after an interval by transfer to the final containers and a 
second pasteurization. Even when the formation of a coagulum in 
the final container is thus prevented, the liquid remains permanently 
turbid and opaque from the presence of considerable quantities of 
suspended colloidal materials, which are unaffected by heating and 
subsequent storage. In the case of a few heavily pigmented varieties 
of grapes, such as the Ives, Concord, Clevener, and other purple 
varieties, the intense coloration of the juices masks their turbidity. 
and renders them attractive to the eye. In most grape varieties, 
however, the juices obtained are densely opaque, tawny yellow, or 
- 
71054°—22——-1 
neces sewer 
