VEGETABLE AND FRUIT DEHYDRATION 133 



Table 13. — Compression of dehydrated fruits mid vegetables 





Mois- 

 ture 

 (per- 

 cent) 



2 



Tem- 

 pera- 

 ture of 

 press- 

 ing 

 (° P.) 



3 



Pres- 

 sure 

 for 

 block- 

 ing 

 (lbs. 

 per 

 square 

 inch) 



4 



Densities (pounds per 

 cubic foot) l i 



Ap- 

 proxi- 

 mate 

 con- 

 tent of 

 pack- 

 ages 

 (lbs. 

 per 

 5-gal- 

 lons) 



8 





Fruit or vegetable 



1 



Initial 

 5 



After 

 com- 

 pres- 

 sion 



6 



Com- 

 pres- 

 sion 

 ratio 

 (tol) 



Reduc- 

 tion in 

 bulk 

 (per- 

 cent) - 



9 



Apple nuggets 



Do 



2 

 2 



25 

 4.1 

 5.7 

 4.2 

 5.2 

 4.8 

 3.7 

 3.0 



28.0 

 6.9 

 4.0 



170 



75 



75 



160 



120 



120 



160 



160 



160 



140 



75 



140 



78 



450 

 850 

 150 

 650 

 650 

 650 

 650 

 650 

 650 

 650 

 150 

 850 

 1,500 



12.5 

 12.5 

 42.0 

 25.0 

 12.5 

 15.0 

 19.0 



6.0 

 10.5 



6.0 

 48.0 

 11.0 

 30.0 



64 

 53 

 79 



62 

 64 

 57 

 62 

 56 

 47 

 61 

 78 

 59 

 60 



5.1 

 4.2 

 1.9 

 2.5 

 5.1 

 3.8 

 3.3 

 9.3 

 4.5 

 10.1 

 1.6 

 5.4 

 2.0 



12.0 

 12.0 

 28.0 

 17.0 



8.0 

 10.0 

 17.5 



8.0 

 10.0 

 12.0 

 36.0 

 12.5 

 27.0 



71 

 64 





44 



Beet cubes .--_-_ . . 



57 



Beet slices. - 



80 



Beet strips _ .. 



72 



Carrot cubes 



50 

 75 



Carrot strips 



Onion flakes 



Prunes, whole ... 



62 

 60 

 27 



Rutabaga slices 3 



68 



Tomatoes, spray-dried juice 4 



31 



1 Densities before compression •were measured on shaken but impressed material (column 5). Densities 

 of commercial shipments are frequently higher. 



2 The percent reduction in bulk equals the difference between the weights of a 5-galion can of compressed 

 vegetables and the corresponding weight of the uncompressed vegetable divided by the former weight. 

 In computing the net weights of packages of the compressed foods, allowance is made for 15 percent of unused 

 space in cans and for 5 percent in cartons. 



3 The tentative moisture content of rutabagas is 5 percent, at which blocking will produce a lower density 

 than that found. 



* Spray-dried tomato-juice cocktail is packed 4 pounds per No. 10 (3 quarts) can. 



the dried fruits and vegetables are low in moisture content. Further- 

 more, with less moisture content any given pressure will produce a 

 higher density and a more cohesive block if the dried product is hot 

 instead of cold. The densities shown in the table were measured on 

 disks one-half to three-fourths inch thick. These disks were kept in 

 cans without wrapping while they cooled, with the exception of onions 

 and carrots, beets, and rutabagas, which were pressed into 1-pound 

 blocks 2% inches thick and were cooled in a holding press. With 

 onions, beets, rutabagas, and carrots it has been found that blocks 

 tightly wrapped in cellophane, with the wrapping sealed, need not be 

 kept in a press to cool. During the cooling the densities under such 

 conditions decrease from 61 to 59 pounds per cubic foot for onions 

 and from 62 to 58 pounds for carrots. 



Sun-dried apricots, cut and pitted, can be compressed by hand at 

 room temperature to a bulk density of 42 pounds per cubic foot. A 

 pressure of 150 pounds per square inch at room temperature has 

 resulted in a density of 79 pounds per cubic foot. Higher pressures 

 and an elevated temperature are required for high densities when 

 fruit products are dehydrated to as low as 2 or 3 percent moisture 

 content. The table shows data on apple nuggets for which, because 

 of a 2 percent moisture content, a pressure of 450 pounds per square 

 inch and a temperature of 170° F. were required to produce a block 

 density of 64 pounds per cubic foot. At 75°, 850 pounds of pressure 

 was required to produce a density of 53 pounds per cubic foot. 



For the K rations used in the Army, fruit bars with 20 percent mois- 

 ture and containing glucose are made by extrusion from machines 

 of the sausage-making type on a belt where the bars are cut to length. 



