22 BULLETIN 1025, U. S. DEPARTMENT OF AGRICULTURE. 
10 per cent more time to pass through the filter, as a result of a 
greater tendency to clog the disk with slime, but gave a slightly 
greater yield of filtered juice than the others, since it was possible 
to reduce the sludge to a drier condition. The juices which had re- 
eeived the preliminary treatment filtered more quickly and with less 
clogging, but the bulky sludges could not be satisfactorily filtered dry. 
In other experiments juices treated with earth were held for 
longer periods at lower temperatures, in order to prevent fermenta- 
tion while allowing sedimentation to become complete. Here one 
encounters a difficulty arising out of the fact that as the temperature . 
at. which the juice is held is lowered, the viscosity of the liquid is in- 
creased, slowing down the rate of sedimentation and making it less 
rapier 
A rather extended series of Soak has shown conclusively. 
that the additional handling necessary and the greater loss of juice 
- resulting from inability to filter the sludges sees a make a ~ 
preliminary treatment with earth followed by sedimentation before 
filtering inadvisable. A larger yield of filtered juice is obtained 
with a smaller expenditure of labor when the juice is allowed to 
stand undisturbed for 12 to 24 hours after pressing in order to allow 
the settling out of cellular débris, then decanted, mixed thoroughly 
with earth, and immediately filtered. 
SEDIMENTATION BEFORE FILTERING. 
A period of sedimentation before filtering is quite necessary and 
should never be omitted if an effort to obtain a perfectiy permanent, 
clear, brilliant filtrate is being made. When either apple or grape 
juice is taken directly from the press, mixed with earth, and filtered, 
the liquid coming through the filter is perfectly transparent. On 
bottling and pasteurizing such juices and allowing them to stand 
for some time, however, cloudiness or haziness appears. The degree 
of the change varies greatly with various fruits, but all juices so 
treated become in some degree turbid colloidal solutions, while in 
some cases a deposit is ultimately formed in the bottles. Check 
samples of the same juices allowed to stand for 12 to 24 hours before 
treatment do not show this behavior, but remain permanently free 
from cloudiness or sediment. 
The explanation of the facts just stated is not known, and only | 
unproved hypotheses can be suggested. When the cells of the fruit 
are ruptured and the juice expressed and exposed to the air various 
constituents are brought together which were previously separated 
from one another in the cells but which are capable of reacting when 
brought into contact. The intercellular materials (pectin and its de- 
rivatives) are brought into contact with the acids of the juices and with 
pectase. It is conceivable that under such conditions a conversion of 
Se 
