16 MASS. EXPERIMENT STATION BULLETIN 404 



GENERAL DIRECTIONS FOR DEHYDRATING VEGETABLES 



Preservation of food is dependent upon the destruction or inactivation of the 

 bacteria, yeasts, and molds which cause spoilage. Growth of these spoilage 

 organisms does not occur when the soluble solids or sugars naturally present in 

 the product are sufificiently concentrated through reduction, by drying or other 

 means, of the water present in the foods. This is the principle employed in the 

 drying of fruits such as figs, dates, prunes, apricots, etc. Also, a reasonable 

 amount of free water is necessary for normal activity of these organisms. With 

 vegetables, which are relatively low in sugar, the moisture content is reduced to 

 a point where there is not enough water to maintain this activity. 



Despite their resistance to attack by molds, bacteria, and other outside or- 

 ganisms, dehydrated foods may still spoil owing to chemical agents within them- 

 selves known as enzymes. These chemical compounds are necessary to the 

 normal life activities of plants, but damaging to their quality as foods if permitted 

 to continue activity after harvesting and storing. When fruits and vegetables 

 become overripe it is due to the activities of the enzymes, which leave an opening 

 for subsequent infection by bacteria and molds. While enzymes are sensitive to 

 heat, they are not always destroyed or inactivated by the temperatures used in 

 the dehydrating process, so special consideration must be given to this factor in 

 preparation. The treatment for inactivation of the enzymes is called blanching. 



Vegetables to be used for dehydration should be dried as soon after harvesting 

 as possible, preferably within a few hours. With the exception of some of the 

 root varieties, most vegetables rapidly deteriorate in flavor and general quality 

 after they are picked. A striking example of this is corn, which within a few hours 

 loses a large part of its flavor and tenderness. 



Equally important is the selection of vegetables at their optimum stage of 

 maturity. The effects of overmaturity or undermaturity are unchanged by 

 dehydrating operations, and while such products might be equal in appearance 

 in the dehydrated form to those prepared from properly selected raw materials, 

 the difference in quality can readily be detected in the flavor and texture of the 

 rehydrated product. 



The general steps in preparing vegetables for dehydration follow very closely 

 the procedures employed in canning and freezing operations. For that reason 

 they will be treated at length only where a more complete understanding of the 

 reasons behind the operation is considered necessary. 



Washing and Trimming 



Since steam is preferable to boiling water for blanching, thorough washing 

 is required. Particular care should be taken with leafy vegetables to remove all 

 sand and grit, since even small amounts will show up markedly in the dehydrated 

 product. Thorough washing will also show up bruises, blemishes, and withered 

 leaves, which must also be removed. Even bruises which hardly detract from 

 the appearance of the raw product will in many instances cause undesirable 

 discoloration in the dehydrated product. 



Peeling 



For home dehydration, hand peeling is the most effective method and results 

 in the least waste. 



