20 BULLETIN" 468, U. S. DEPARTMENT OF AGRICULTURE. 



starch to sugar seems to be associated in a general way with seasonal 

 changes in temperature. In sweet potatoes kept in cold storage (4° 

 C.) there is a rapid disappearance of the starch and an accompanying 

 increase in cane sugar. It is a matter of common experience that 

 late in the season sweet potatoes are apt to deteriorate in quality and 

 sometimes develop a disagreeable taste, especially if they have been 

 left in a cold place. The peculiar and characteristic flavor often 

 noted is due to a fungus disease resembling dry rot. These unde- 

 sirable changes may take place at any temperature below 50° F. To 

 lessen the danger of shipping in cold weather, the southern sweet- 

 potato crop is usually sent north early in the autumn and stored near 

 the retail market. 



In choosing sweet potatoes at the market, firm, fresh-looking ones 

 should, of course, be preferred to the old and shriveled roots, and 

 medium-sized, regular-shaped roots are more satisfactory than very 

 large, very small, or irregular ones, for they cook more evenly, 

 give less waste in paring, and are of better size to serve. Early in 

 the season unripe sweet potatoes are sometimes marketed and may 

 be recognized by cutting them; the flesh will soon turn dark green, 

 whereas in the properly ripened roots it will not change color. 



COOKING. 



The changes which cooking makes in sweet potatoes are, in general, 

 similar to those in white potatoes. One special point is generally 

 noticeable — the longer the cooking is continued, the more moist does 

 the root become. This is probably because part of the starch is made 

 soluble by the heat and then dissolved in the juice, while the cane 

 sugar is split up into simpler sugar. The very sweet southern 

 varieties become so moist during baking that a sirup frequently oozes 

 through the skin. 



There are many different ways of preparing sweet potatoes for the 

 table, the most common being simply boiling or baking. They are 

 also fried, cooked with sugar and butter (when they are commonly 

 called "candied"), used in making pies, like pumpkin or squash, or 

 in other made dishes. 



DRIED AND CANNED SWEET POTATOES. 



Dried sweet potatoes were formerly prepared at home, and strings 

 of them were hung from the rafters along with apples and other 

 drying fruits and vegetables, but in these da} T s of storage Ava rehouses 

 the custom has verylargely passed away. Special devices for evapo- 

 rating sweet potatoes are on the market, and desiccated sweet pota- 

 toes prepared in much the same way as desiccated white potatoes are 



