% 
DEHYDRATION OF FRUITS AND VEGETABLES 27 
becomes evenly distributed. This period of curing will usually take 
several weeks. An alternative method used in the Bureau of Chemis- 
try is to place the dried product in large friction-top cans for curing, 
thus insuring complete protection from contamination and insect 
infestation. 
Leafy vegetables, like spinach, must remain in the drier until the 
moisture content of the stems is very low. At this point the product 
is bulky and the leaves are brittle. For economy in packing and 
handling it is desirable to reduce the bulk by compression. For 
this purpose the leaves are exposed to currents of cool damp air 
until they have reabsorbed just enough moisture to make them 
slightly flexible. 
INSECTS ATTACKING DRIED FRUITS ” 
From an economic standpoint the most serious type of spoilage 
after drying is due to insect infestation. Parker (40)? has studied 
the insect pests of dried fruits. The most serious insect pests, in 
the order of their importance, are the Indian-meal moth (Plodia 
interpunctella Hbn.), the saw-toothed grain beetle (Silvanus surina- 
mensis L.), and the dried-fruit beetle (Carpophilus hemipterus L.). 
The Indian-meal moth and the saw-toothed grain beetle are primarily 
pests of grain, grain products, and nut meats, which, coupled with 
the fact that they are cosmopolitan in distribution, insures their 
Seeks distribution not only in all kinds of establishments manu- 
acturing and storing such commodities but also in retail stores and 
private homes. They are consequently present nearly everywhere, 
ready to infest dried fruits whenever the opportunity is presented. 
The Indian-meal moth is by far the most injurious because in the 
larval stage it spins much webbing, causing the fruit and the con- 
tainers to become webbed and badly polluted with excrement. These 
are the outstanding evidences of infestation, which immediately 
catch the eye of a purchaser. 
The insects which attack dried fruits pass through the usual 
insect life cycle. That is, the parent insect, whether it be a moth 
or a beetle, lays many eggs. From the eggs hatch the worms or 
rubs, which in turn ultimately pass into a chrysalis or pupal stage, 
rom which the adults of the next generation emerge. In warm 
weather this life cycle, representing one generation, is passed in 
approximately one month. During colder weather the life cycle may 
be greatly prolonged, sometimes covering three or four months. 
PREVENTIVE MEASURES 
Even if the fruit is not directly attacked by insects it is important 
to prevent infestation, so that the agen will not be polluted by 
webs and excreta. Preparation by lye dipping, sulphuring, or proc- 
essing is supposed to kill all insect life in the fresh material. In 
the case of fruit packed in well-sealed containers, insect infestation 
practically always comes from eggs laid by adult insects on the 
product between the time it is removed from the drier and the 
2 Prepared by E. A. Back, Entomologist in Charge of Stored Product Insect Investigations, Bureau of 
Entomology. was 
3 Italic numbers in parenthesis refer to the bibliography, p. 39. 
7 , : 
