VEGETABLE AND FRUIT DEHYDRATION* 209 



used on either raw or steamed sweetpotatoes ; the waste in peeling and 

 trimming will run from 15 to 30 percent for sound materials. Hand, 

 brine, or lye peeling can be used with considerable reduction in losses. 



Sweetpotatoes are cut into slices, cubes, or strips. Government 

 purchase specifications limit cubes to the three-eighths-inch dimen- 

 sion. Immediately after cutting, the pieces should be washed 

 thoroughly by strong sprays of clean cold water in order to remove 

 starch from the cut surfaces. If not blanched immediately, the cut 

 material should be kept under running cold water or in a 2 percent 

 salt solution. For material on which this treatment has not proved 

 effective the use of a 1 to 2 percent citric acid solution has been 

 recommended. Citric acid is not, however, readily available. In any 

 case, the material should not be held for more than 1 hour before 

 blanching. 



If the sweetpotatoes are to be riced or powdered, they are pre- 

 cooked before they are dried. To make the riced product, the sweet- 

 potatoes are given the same preliminary treatment as potatoes, except 

 that instead of being cut in pieces, the whole tubers are steamed until 

 thoroughly cooked. The cooked product is then passed through a 

 ricing device having holes not over one-eighth inch in diameter. If 

 the ricing is done while the potatoes are hot, there is less tendency 

 for the strings to stick together. The strings should fall from the. 

 ricer to the drying surface. 



Sweetpotatoes should be blanched as soon as possible after they 

 are peeled and cut. Blanching in steam is recommended. The time 

 must be adjusted to allow complete destruction of the peroxidase sys- 

 tem, which requires 6 to 10 minutes (table 21) . It is essential to avoid 

 all contact with iron during blanching. Failure to observe this pre- 

 caution will result in blackening of the product. A suggested 

 blancher loading is shown in table 21 (p. 181). The maximum delay 

 allowable between blanching and dehydration is 1 hour. 



Information on the moisture content of fresh sweetpotatoes and on 

 drying ratios and conditions suggested for dehydration is contained 

 m tables 22 to 25. Table 26 contains information on packaging 

 Dried sweetpotatoes are considerably less affected by heat and moisture 

 than are dried potatoes. For export 5-gallon cans or lead-foil- 

 protected cartons, without gas packing, are used. 



The rate and effectiveness of rehydration of sweetpotatoes can be 

 determined by obtaining the drained weight of the rehydrated sample 

 at various intervals of time and temperature in water. * To obtain this 

 drained weight add six parts of Avater to one part by weight of sliced 

 sweetpotatoes and boil gently for 30 minutes. Drain carefully 

 through an 8-mesh strainer for 2 minutes and weigh. The rehydrated 

 weight should be approximately two or three times the original weight 

 of the dried vegetable. Rehydrated sweetpotatoes should be sweet, 

 tree from bitter, strong, or sour taste, mild in sweetpotato flavor, and 

 sort and tender m texture. Their color should be that of cooked f resh 

 sweetpotatoes of the same variety, free from dark spots and streaks. 



Soaking before boiling will give a plumper product and slightly 

 greater drained weight. Longer boiling may cause deterioration in 

 taste, flavor, and color. Products that have been stored for some time 

 at 90° F. may absorb water more slowly than freshly dried material. 



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