MISC. PUBLICATION 5 4 0, U. S. DEPT. OF AGRICULTURE 



Page 



Substitutes for tin-plate containers 129 



Functions of the package 130 



Single sheets, double laminations, and 



compound laminations 131 



Glaze packaging for compressed dehy- 

 drated foods 132 



Compression to high density for packaging ... 132 



Presses and processes 134 



Holding presses 137 



Sanitation 137 



Water supply _-_ 139 



Waste disposal 139 



Operating personnel 140 



Control of insects and mites 141 



Fumigation 141 



Sprays 141 



Temperature and moisture 142 



The control laboratory 142 



Examination of raw product 143 



Moisture determination 144 



Determination of adequacy of blanching-. 147 



Vitamin determinations 150 



Determination of sugar (vegetables) 153 



Determination of starch (vegetables) 155 



Determination of sulfur (dried fruits and 



vegetables) 156 



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The control laboratory— Continued. 



Analysis of atmosphere in cans of de- 

 hydrated vegetables 157 



Rehydration tests 159 



Methods _ 160 



Sources of error 161 



Composition and amount of water 162 



Serial tests 164 



Nature and condition of material 166 



Definition of terms 167 



Summary of rehydration tests 169 



Quality testing 169 



Procedure for quality tests 171 



Jury selection and training 171 



Summary of quality testing 172 



Processing costs 172 



Labor requirements 172 



Segregation and analysis of processing 



costs 173 



Packaging and warehousing costs 181 



Indirect and overhead costs- 181 



Estimated processing costs in vegetable de- 

 hydration 182 



Handling various vegetable and fruit crops... 183 



Vegetables 183 



Fruits 210 



Literature cited. 216 



INTRODUCTION 



More than a year before the attack on Pearl Harbor military 

 leaders and food technologists in the United States realized that 

 technical information on the dehydration of foods might become 

 vitally important. As a result of the war, the production of de- 

 hydrated foods has increased rapidly. Prior to the year 1941 only 

 relatively small quantities of a few vegetables were dehydrated com- 

 mercially, but at present vegetable dehydration has become a large 

 industry. The dehydration of fruits has been a well-established and 

 important industry for many years and considerable published infor- 

 mation on the subject, including results of investigations by this 

 Bureau, is available. The part of this manual dealing with fruits 

 is not intended to be a complete guide for operators in the dehydra- 

 tion of fruits but presents only some of the most salient points of 

 common information which may be of incidental interest to vegetable 

 dehydrators. The developments in the dehydration field have been 

 accompanied by large advances in the production of dehydrated 

 milk, eggs, and meat. 1 



In 1940 the Bureau of Agricultural and Industrial Chemistry 

 started new investigations on the dehydration of foods. The objec- 

 tives were to discover (1) methods of decreasing the weight of 

 foods, (2) ways of saving shipping space, (3) types of containers 

 requiring less metal, (4) how to lengthen the storage life of dehy- 

 drated products, (5) techniques for retention of the greatest possible 

 nutritive value of the foods. 



Two dehydration training schools were conducted by the Bureau 

 to assist the many food manufacturers who were engaged in, or about 

 to become engaged in, the dehydration of vegetables and fruits. The 

 first school, lasting 2 weeks, was held at the Western Kegional 

 Research Laboratory, Albany, Calif., in September 1942; and the 

 second, lasting 2 weeks, was held in Rochester, N. Y., in October 



1 The term "dehydration" is commonly used to denote specifically a controlled process of 

 drying with forced circulation of heated air. 



