VEGETABLE AND FRUIT DEHYDRATION 211 



fruits may be washed under sprays or by immersion while moving on 

 a belt. Growers with small quantities commonly wash fruit in boxes 

 by immersion. Rotary washers should not be used for tender -fleshed 

 fruit. 



Blanching is seldom used in the preparation of fruits for drying, 

 but is advisable for apricots, nectarines, peaches, and pears if they 

 are to be dehydrated rather than sun-dried (&£). Prunes and some 

 grapes are commonly dipped in hot lye solution as a means of making 

 fine breaks in the skin ; this effect, referred to as checking, facilitates 

 drying. The treatment is not however a blanching operation — that 

 is, a thorough penetration by heat. For the most part, large pieces 

 or whole fruits are dried, in contrast to the thin slices, cubes, or strips 

 of vegetables. Fruits contain large quantities of juice, and when 

 blanching is used it must be carefujly controlled to avoid excessive 

 loss of juice, called bleeding. 



Blanching in a manner similar to that used with dehydrated vege- 

 tables has been suggested for certain cut fruits that are to be de- 

 hydrated, as a means of improving quality from the standpoint of 

 cleanliness, freedom from insects, superior vitamin retention, and 

 better appearance. Sulfuring is, however, standard commercial pre- 

 treatment for the lighter colored fruits, such as apples, apricots, 

 golden-bleached raisins, peaches, pears, and nectarines. Prunes and 

 figs are very rarely sulfured. Fruit is usually sulfured in a sulfuring 

 house while on trays stacked on trucks. The trays must be nonmetallic. 

 The trucks occupy most of the space but there must be sufficient open 

 space to permit free circulation of the fumes. It is advisable to burn 

 sulfur in a shallow iron pan placed at or slightly below the floor level 

 between the entrance and 1 the nearest truckload of fruit. The amount, 

 of sulfur burned and time of sulfuring varies with the type and condi- 

 tion of the fruit (28, 33) . Exposure of sulfured fruit to sunlight for 

 a few hours before it is put into the dehydrator is sometimes used as a 

 means of improving color but this is not necessary if blanching is used. 



Most of the commercial fruit dehydration industry is located along 

 the Pacific coast. In areas where sun drying is feasible — particularly 

 northern and central California — it is used as well as dehydration. 

 Apricots, peaches, pears, and raisins are for the most part sun-dried. 

 Apples are dried in large quantities in New York and Washington and 

 cranberries are dried chiefly in New England. 



Mechanical fruit driers have gone through a long period of develop- 

 ment, and a large number of older types and designs are still in use. 

 During the later years of World War I and in the period that followed, 

 a number of new commercial makes of driers were introduced, chiefly 

 of the tunnel type with forced draft, In California, where sun drying 

 is common, the mechanical drier was originally looked upon as "rain 

 damage insurance," and, although rains are infrequent there during 

 the drying season, a series of rains, such as the destructive wet 

 spell of 1918, could cause enormous losses. Size of operation and conse- 

 quently size of mechanical installation varies, with capacities ranging 

 from a few tons daily to 100 tons or more. The mechanical equipment 

 also varies with the type of fruit ; a prune drier, for example, differs in 

 certain respects from other types. The type most generally used is the 

 counterflow tunnel with varying methods of heating, air flow, and air 

 propulsion. The fruit is conveyed on trays loaded on trucks. 



