18 MISC. PUBLICATION 524, U. S. DEPT. OF AGRICULTURE 



each 1 percent of decrease in moisture content. This relationship held 

 over a range in moisture content of 12 percent to 3 percent. That is, 

 within that range each successively lower percentage of moisture 

 lengthened the storage life of the cabbage 50 percent. A similar rela- 

 tionship has been observed between palatability and moisture content 

 of carrots during storage. 



Moisture pick-up, or the moisture that accumulates within a package 

 after it has been sealed, is not serious if it does not exceed 2 percent 

 in a year. An increase in moisture no greater than that will not cause 

 excessive deterioration. Measures that protect sealed and stored 

 packages from high temperature and dampness are of value. Dehy- 

 drated vegetables and fruits — in fact all foods, fresh or packaged — 

 keep better at low than at high temperatures. 



Safeguards against insect infestation and damage by rodents are 

 necessary. Foods leaving the clehydrator will remain free of insects 

 if run directly into clean packages that are immediately sealed. If 

 dehydrated foods are left exposed, insects may lay eggs on them, and 

 unless they are heated again to 135° F. before being packaged, active 

 infestation may be sealed in the package and ruin the product. If 

 the food has become infested with insects, heat treatment will not 

 make it fit to use. Insects cannot live in packages containing inert 

 gas. Rodents are a constant threat to nonmetallic packages of food. 



Compressing Dehydrated Vegetables 



Compressing dehydrated vegetables makes possible additional sav- 

 ings in space of 40 to 80 percent. It takes out most of the air and 

 simplifies packaging. Pressures of 100 to 2,500 pounds per square 

 inch are used. 



Meat compresses more readily than other dried foods, and blocked 

 (pressed) dehydrated pork is being purchased for lend-lease ship- 

 ments. Compressing egg powder reduces the volume 30 percent. 



Advances have been made in producing dehydrated carrots, 

 rutabagas, onions, and beets in compressed form. Because of the 

 possibilities of saving shipping space the Army and other agencies 

 purchasing food for shipment abroad are much interested in these 

 developments. Dried vegetable material, however, has a tendency 

 to shatter under pressure at room temperature unless more moisture 

 is present than is permissible in dehydrated vegetables. If material 

 is compressed at a higher moisture content than 5 to 7 percent, it must 

 be dried further, which takes a long time and is destructive of vitamins. 

 Compression may break down the cell walls of starchy vegetables and 

 cause release of starch, so that potatoes, for example, may have a 

 pasty taste and consistency when reconstituted. 



Research by both Government and commercial investigators is 

 producing encouraging results. Applying pressure at 120°-165° F. 

 shows promise of preventing the shattering of vegetables, and a 

 method of dehydrating and compressing some products at freezing 

 temperatures is attracting considerable interest. 



Drying and Sulfuring Fruits 



In areas of abundant sunshine and freedom from rain during and 

 following the harvest season, such as are found chiefly in California, 

 certain fruits are extensively sun-dried. Other fruits are artificially 



mm 



