DEHYDRATION OF VEGETABLES 17 



Subdividing 



Since dehydrat'on is achieved mainly by surface evaporation, the greater the 

 surface of the product, the more rapid is the drying process. Tubers and root 

 vegetables are therefore sliced, diced, shredded, or riced, which not only facilitates 

 drying, but also gives a product of distinctive appearance. Dicing or cubing is 

 not recommended because of the resulting waste of product and the added time 

 required for dehydration and rehydration. Slices and shoe-string or julienne 

 style pieces have been found most satisfactory for both dehydration and rehy- 

 dration. Slices should not exceed 3/16 of an inch in thickness, and products cut 

 in julienne style should be no larger than this in cross section. 



Traying 



To facilitate handling of the products after dehydration, and to prevent dis- 

 coloration of the material through contact with residue left by other products 

 previously dehydrated, the trays should be covered with a single layer of cheese- 

 cloth. Absorbent gauze, 28 X 24 mesh of 36-inch width, has been found ideal for 

 this purpose. Each 15-inch double thickness section will provide ample material 

 to cover four trays of the small dehydrators, and each piece can be used several 

 times for the same product. 



In loading the trays, care should be taken to allow for intimate contact of the 

 air with the individual pieces of product, and adequate circulation around them. 

 With sliced or julienne style products the shape of the pieces will take care of this 

 to a great extent, and most care should be given to spreading the product uni- 

 formly over the trays. With leafy vegetables, such as spinach or chard, on the 

 other hand, the pieces should be so arranged that matting will not take place 

 during subsequent operations. 



Blanching 



The blanching process consists of heating the material in hot water or prefer- 

 ably live steam for a suitable length of time. While the primary purpose of this 

 treatment is to inactivate the enzymes, at the same time it serves several other 

 functions as in canning and freezing. During the process certain disagreeable 

 odors and flavors are driven off, and with some products, such as snap beans, the 

 waxy outer covering of the product is removed. 



In the course of the treatment the product is also partially precooked, which 

 not onl> sets the color, but also hastens the drying time by softening the tissues 

 and allowing a more rapid diffusion of moisture from the cells. Equally important, 

 the precooking also facilitates rehydration of the material for serving. While 

 in some cases only a relatively short time is required to inactivate the enzymes, 

 the resulting improvement of flavor, texture, and appearance make a longer 

 blanch desirable in many instances. For some vegetables a satisfactory length 

 of blanch is almost sufficient to cook them, and only a short cooking period is 

 required in preparing the product for the table. While prolonged blanching may 

 cause increased loss of the water-soluble constituents and some of the vitamins, 

 the storage qualities are definitely improved. Insufficient blanching, on the other 

 hand, results in a definite lowering of quality. Improperly blanched products 

 rapidly lose their color, and develop off odors and flavors. Spinach, for example, 

 when improperly blanched, becomes a dirty gray color on storage and takes on a 



