4 BULLETIN 1335, U. S. DEPARTMENT OF AGRICULTURE 
SELECTION OF MATERIAL 
The fresh material must be so solid that it can be spread in a 
whole or divided condition on wire-screen or wooden-slat drying 
trays. It must also lend itself to mechanical or rapid hand opera- 
tions during preparation. Finally, the resulting product must be 
of good quality. The following fruits meet these specifications: — 
Apples, apricots, cherries, cranberries, grapes, loganberries, peaches, 
pears, prunes, and raspberries. The following vegetables meet them: 
Beans (string), cabbage, carrots, celery, corn (sweet), horseradish, 
onions, parsnips, potatoes, pumpkin and squash, spinach, and 
turnips. Cabbage, carrots, celery, parsnips, potatoes, and turnips 
are important principally as soup-mixture ingredients. - 
Dehydration does not improve the quality of fresh fruits or vege- 
tables, nor does it satisfactorily utilize unsound foods. At best 
the process can only conserve the original constituents of the foods, 
minus replaceable water. Not only does the condition of the fresh 
material affect the quality of the product, but the waste in sorting 
and trimming, together with the labor involved in preparation, 
affects the cost of the prepared material. One of the future eco- 
nomic benefits of dehydration probably lies in the more complete 
utilization of fresh and sound cull or second-grade fruits and vege- 
tables, so classed because of their size or shape. 
As a general rule, fruits and vegetables are most suitable for. 
dehydration when the flavors are most satisfactory and the texture 
remains tender and succulent but firm. Fruits which are fully ripe 
but firm are preferable. Vegetables with color and texture suitable 
for table use are desirable. Dehydration kills the living tissues and 
prevents further ripening of the product. 
PREPARATION OF MATERIAL 
Careful handling reduces labor and waste. Bruised tissue is 
especially susceptible to discoloration and decay. Individual pieces 
prepared from good stock are also more uniform and attractive than 
those from heavily trimmed stock. 
WASHING 
Raw materials should be as carefully washed and cleaned for 
dehydration as for table use. Much of the washing machinery 
used in canning is suitable for dehydration. A rotary cylindrical 
washer equipped with a water-spraying system is very satisfactory 
for washing many types of products. Soft or easily broken fruits 
and vegetables may be washed by passing the trayed material on 
an endless belt between several sprays of cold water. 
GRADING FOR SIZE 
The segregation of fresh fruits and vegetables according to size 
facilitates both the preparatory handling and the drying. 
One type of grader consists of a perforated metal plate, 3 by 10 
feet or larger. The perforations are in sections of varying size, and 
the plate 1s inclined and mechanically agitated in order to insure 
an even ‘“‘flow”’ of the material in one direction. The product is 
separated according to size by being passed through the perfora- 
