26 BULLETIN 1335, U. S. DEPARTMENT OF AGRICULTURE 
fruit seems soft, mushy, or wet, and sticks together when the pressure 
is released, the moisture content is probably 25 per cent or more. 
If the fruit is springy and when the pressure is released separates in a 
few seconds to form pieces of approximately the original size and 
shape, the moisture content is usually about 20 to 25 per cent. if 
the fruit feels hard or horny and does not press together, falling 
apart promptly when the pressure is released, the moisture content 
is probably below 20 per cent. 
At the proper stage of dryness vegetables look thoroughly dry and 
are often hard or crisp. 
The Association of Official Agricultural Chemists has published a 
water-oven method for the determination of moisture in dried 
apples and a vacuum-oven method for its determination in all dried 
fruits. Although the water-oven method gives accurate results only 
for apples, it gives relative results, valuable for factory control 
purposes, on other products. The vacuum-oven method gives suf- 
ficiently accurate results on all dried fruits and vegetables, but it 
requires more time and more expensive equipment than the other 
method. 
In using either method care must be taken to select a composite 
sample from different portions of the lot, so that it will be representa- 
tive of the lot as a whole. The sample is ground as fine as possible 
and kept in a sealed glass jar or tin can until used. 
Water-oven method.—Weigh 5 to 10 grams of sample into a metal 
dish about 8.5 centimeters in diameter, provided with a cover, and 
break down all large lumps. Place the dish on the shelf, not the 
bottom, of an oven having a vent on top to afford ventilation. 
Dry for four hours at the temperature of boiling water, not lower 
than 96° C. Replace cover, cool in a desiccator, weigh, and compute 
the loss in weight as percentage of moisture.? 
Vacuum-oven method.—Weigh 5 to 10 grams of sample into a metal 
dish about 8.5 centimeters in diameter, provided with a cover, and 
break down all large lumps. Dry in a vacuum oven at 70° C. for 12 
hours at as low a pressure as possible, not to exceed 4 inches (100 
millimeters) of mercury. During the drying, admit to the oven a 
slow current of air, about 2 bubbles a second, dried by bubbling 
through concentrated sulphuric acid. The metal dish must be placed 
in direct contact with the metal shelf of the oven. Replace cover, 
cool in a desiccator, weigh, and compute loss of weight as percentage 
of moisture. Disregard any temporary drop of oven temperature 
which may occur during the forepart of the drying period owing to 
rapid evaporation of water. With raisins and other fruit rich in 
sugar, use about 5 grams of sample and about 2 grams of finely 
divided asbestos dried with the dish. Moisten with hot water, mix 
sample and asbestos thoroughly, evaporate on the water bath barely 
to dryness, and complete drying. 
CURING 
Products are never uniformly dry when removed from the drier. 
Large pieces and pieces not as directly exposed to the currents of 
heated air as most of the material contain more moisture than the 
rest. The products should be stored in large bins until the moisture 
1 Dried peaches should be dried 41% hours; apricots, 314 hours; and pears, 5 hours. 
. 
