VEGETABLE AND FRUIT DEHYDRATION 137 



the time required for cooling thick blocks of carrots in air is afforded 

 by these test data : A block 2y 2 x 1% x 6% inches of compressed, diced 

 carrots cooled at the center from 140° to 90° F. in 3 hours, in air 

 at 80°. The block was cellophane-wrapped, confined in a holding 

 press, exposing the narrow sides and ends only. Bemoved at 90°, it 

 held its shape. 



Two-pound blocks of diced carrots were formed in a mold 6!% 2 x 

 4% inches of a suitable depth. The conditions were 160° F., 1,200 

 pounds per square inch, and a 30-second period at that pressure. The 

 blocks were removed, wrapped in paper and cellophane, and sealed. 

 After compression the dimensions over the wrapping were 6 1 % 2 x ^Vz 

 x 2% 6 inches. The expansion in a direction perpendicular to the 

 movement of the ram was % 2 inch on a 6%-incn length, with allow- 

 ance for thicknesses of paper and cellophane. The immediate expan- 

 sion parallel to the movement of the ram was three-eighths to one-half 

 inch. An additional expansion resulted before it was stopped by the 

 wrap and by air cooling. Holding presses prevent the latter 

 expansion. 



Actual practice will be a compromise between the goal of most de- 

 sirable density, on the one hand, and, on the other, the obtainable 

 equipment and its economic adaptation to use. A diagrammatic 

 sketch of a packaging press is shown in figure 67. 



Blocks should be wrapped and sealed at once in kraft paper or cello- 

 phane. If the packing case is large enough to permit slight swelling 

 of the blocks, they may be packed immediately but if very close ad- 

 herence to the dimensions of the mold is required, the blocks must be 

 cooled under light pressure, part way to room temperature. 



If compression is carried out with the wrapper inserted in the mold, 

 complete cohesion of the block is not required. With this latter 

 method of compression and wrapping, the wrapper must maintain its 

 integrity as a moisture-vapor resistant sheet without tears, pinholes, 

 or other breaks. 



Holding Presses 



The use of holding presses for the purpose of fixing the shape and 

 dimensions of tobacco plugs and blocks of dried hops, catnip, and 

 sage is well known. The time required for tobacco is 5 days; for hops, 

 12 hours. Such holding presses are not heavy or expensive, because 

 little pressure is used. In one form a hardwood frame of rectangular 

 shape is used. It has a solid bottom end and a loose top end. Plugs 

 are stacked in it nearly to the top, the loaded frame is placed under 

 a small screw press, the top pressed down, wedges are inserted above 

 the top and against the top of the frame, and then the pressure is 

 released and the loaded frame is removed. This type of press, with 

 spaced blocks for ventilation, is one suggested way to cool under 

 pressure. 



SANITATION 



A primary essential in a dehydrating plant that is endeavoring 

 to make products of the highest quality is the maintenance of suit- 

 able standards of plant sanitation. Among the important factors 

 affecting plant sanitation are building construction, equipment, access 

 of rodents and other pests, storage facilities, water supply, waste 

 disposal, and, most important of all perhaps, the operating personnel. 



