210 MISC. PUBLICATION 5 4 0, U. S. DEPT. OF AGRICULTURE 



Soaking before boiling will compensate for this more satisfactorily 

 than will increasing the time of boiling. There is a tendency toward 

 disintegration of pieces when boiled 30 minutes, but a raw taste and 

 flavor may result from shorter boiling. 



TOMATOES 



Tomatoes are widely grown and rank first among crops that are 

 canned. They are highly nutritious and comparatively easy to pro- 

 duce ; they yield well and are consumed in large quantities. Dehydra- 

 tion of tomato slices of fleshy varieties in the types of equipment 

 used for other cut vegetables is possible, but the product is hygroscopic 

 and does not keep well except in tightly closed cans. Tomato puree 

 can be dried on drum driers and juice can be spray-dried to form a 

 powder. There is considerable interest in the latter products but 

 thus far commercial production has not been developed. Progress 

 has been made with the technical problems of tomato dehydration, 

 but because of the high water content of tomatoes the method is not 

 highly feasible from the economic standpoint. Moreover, tomatoes 

 and tomato juice can be easily preserved by canning in glass containers, 

 of which there is an ample supply. 



Fruits 



The information presented here on fruits is concerned chiefly with 

 dehydration in tunnel and cabinet dehydrators, by means of currents 

 of heated air. Sun drying, evaporation in kilns, spray drying, vacuum 

 drying, and other methods are also, in greater or less degree, estab- 

 lished commercial methods of producing dried fruits or dried-fruit 

 products, and some of these methods are also applied to vegetables. 

 Although the chief purpose of this publication is to deal with the 

 use of tunnels and cabinets particularly in vegetable dehydration, 

 similar equipment is used for fruits. For technical guidance in the 

 dehydration of fruits other sources should be consulted (7, 9, 11, 13, 

 36, J+6, Jft), and Circular 619 (9) gives an extensive bibliography. 



Most fruits should be harvested frequently and then dried as soon 

 after harvest as possible. Apples, apricots, cherries, peaches, pears, 

 and nectarines should be picked from the trees and not allowed to 

 fall to the ground. Prunes are harvested from the ground two or 

 three times during each season. The trees are shaken for the second 

 and third pickings. Figs are harvested from the ground and are 

 usually one-third to two-thirds dried when harvested. Grapes are 

 harvested from the vines by pulling or cutting off the bunches. All 

 of the softer small fruits require special care in handling and will 

 tolerate very little storage; such fruits are not dried commercially 

 in large amounts. Apples, pears, and cranberries can be stored over 

 fairly long periods; pears must be dried as they ripen in storage. 

 Citrus fruits have the advantage of good keeping quality in storage ; 

 drying of citrus fruits, however, is still in the experimental stage. 



Although high-quality fruits yield the best dried products it is a 

 common practice to dry packing-house and cannery culls. All fruits 

 should be carefully Avashed. Apples and pears can be washed at 

 the time of spray residue removal in a continuous machine. Other 



