16 misc. publication' 5 2 4, u. s. dept. of agriculture 



Packaging and Storage 



The packaging of dehydrated foods presents many problems. The 

 dry material is normally surrounded by air in the package. Air con- 

 tains oxygen, and the presence of oxygen in containers may result in 

 oxidation of the food. This is a deteriorative process that varies in 

 rate with the commodity, its moisture content, the temperature, length 

 of time the product is kept in the package, and other conditions. 

 Oxidation may cause loss of color, flavor, and nutritive value. Some 

 dehydrated foods keep well in air ; others require that air be excluded 

 almost completely. 



FlGTJKE 8. 



-Shredded cabbage carefully spread on trays which are being piled up 

 ready to go into the drier. 



Replacing the air in a package of food with an inert gas — in this 

 case, one that contains little or no free oxygen — has been found to 

 retard the loss of desirable factors in certain dehydrated foods that 

 are particularly subject to oxidation. Studies have shown that inert- 

 gas atmospheres are especially necessary for carrots and cabbage. 

 Specifications for Government purchase require gas packing for these 

 two vegetables. 



The inert gases recommended are carbon dioxide and nitrogen. The 

 carbon dioxide is usually preferred because it is less expensive than 

 nitrogen. The air in the package is replaced with gas in various ways. 

 The can of food may be placed in an airtight chamber and the air ex- 

 hausted; when a high vacuum is reached the gas is allowed to flow 

 into the chamber and fill the can, which is then sealed. Another 



