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UNITED STATES DEPARTMENT OF AGRICULTURE 
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Washington, D. C. September, 1925 
COMMERCIAL DEHYDRATION OF FRUITS AND VEGETABLES 
By P. F. Nicuo.s, Investigator in Commercial Dehydration, Ray PowErs, Junior 
Chemist, and C. R. Gross, Junior Chemist, Laboratory of Fruit and Vegetable 
Chemistry, and W. A. NoE.L, Associate Development Engineer, Office of Develop- 
ment Work, Bureau of Chemistry 
CONTENTS 
Page Page 
Preservation by dehydration________________ 1 | Drying—Continued. 
Weanvaranowlnaustry.ss--2.l¢-20 eed 2 Gil} See Pk Bee Te eer are See toe E 13 
MEL GranOnDlanbeass-ceee Nk Sele 2 1 gn PN ah AE richest ERI ye i nes Te ies 15 
Selection of materials. Soe ie sisirh) ps6) 4 Mroistiretin thetair iret shia ta 15 
Brepanationofmateriale 2. 2-2 ea 22 4 Relation of drying conditions to drying 
Vas lain orks Lode EAE ee EY a Da 4 rate and quality of product____________ 17 
(rAGIN EOF SinG ap. Vee per oe eee des 4 Recinculapions see) yee es ae pe 17 
eve Tita y ce set ag ae pe ioe ha med CE Sine 5 Engineering calculations for designing a 
AN pheercoviclume alee OWLS shee oie eee eee este 6 rien’) yeep iy ett Peal eee ee 21 
heck Ce sen eet Sais eA 8 oe 6 End point of dehydration_______________ 25 
Subdividing ts Are aT Ag DSP! GP tCuring. see eae AN Ake RAR ae ee 26 
iRinhing and! seeding 24... 45 ake ee 7 | Insectseattacking dried fruits_______________- 27 
Draying =: oe PPE See as, Met PUAN 2 8 Breventive Measuress oe. sss eee 27 
Conveying the trayed material______________ 8 Remedial measuress 22 Sis ei ers 28 
IPEPLECAUIMENL! = Ayers ae es Se Packinge and ston gis 2m en kee 29 
Blanching or processing________________- 9 | Detailed directions for drying_______________ 31 
Sulphuring. 5212 se SE pe od Ao ee 10 rin tigate at oy poe 2 TN 7 ee 31 
AD TNyA ET ee serie pr eee wena ae Meagher wrt ge 10 Veretablese otha. stakes Soule eae 35 
Hguipmienta 77 tit So ih. er eres ay HOM? Bibliography 2s. 28s et. 2 eek ee eee ee 39 
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PRESERVATION BY DEHYDRATION 
Spoilage of raw food is due principally to the growth of molds 
and bacteria. This growth does not occur when the soluble solids 
are sufficiently concentrated by the reduction, by drying or by other 
means, of the water present in foods. Even if they are not killed, 
the molds and bacteria remain dormant and harmless in the absence 
of a suitable medium for their growth. Changes in composition, 
flavor, and appearance, however, may also be brought about by the 
action of the enzymes present in practically all foodstuffs. As 
these ferments are not always destroyed by the treatment which 
stops mold and bacterial action, they must be considered in working 
out methods of dehydration. 
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Notr.—This bulletin is intended primarily for the use of those who either have decided to enter or are 
already in the dehydration industry. The information here given will enable beginners to proceed with 
a fair assurance of being able to prepare satisfactory dehydrated fruits and vegetables and it will assist those 
now engaged in the work to improve their methods. eh : 
The investigation here reported was undertaken to determine certain physical principles and their 
adaptation to dehydration problems in general. The project was discontinued before it was possible to 
consider the modifications necessary for the different varieties of fruits and vegetables. Factors leading 
to the deterioration of dehydrated products and the relation which the condition and the variety of fruits 
and vegetables may bear to this deterioration, important phases of the preblem not here considered, are 
being investigated in the Bureau of Plant Industry, 
38850°—25t—Bull. 1335——1 
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