A STUDY OF SWEET POTATO VARIETIES. 5 



canned product it is extremely desirable to know something about 

 them. Shiver {18), McDonnell (15), and Keitt {11, 12, 13) have 

 shown that the sweet potato has a high starch content, with some- 

 what variable quantities of cane sugar and dextrose. The analj^ses 

 of these writers show the content of starch to vary between about 

 10 and 29 per cent in the freshly dug potatoes, the average being 

 approximately 20 per cent. Considerable diiferences in this respect 

 are noted in the varieties at the time of digging. Keitt {12, 13) 

 has given special attention to the moisture content and to the pro- 

 portions of the various carbohydrates in sweet potatoes when dug 

 at different stages of maturity. He notes that in the small potatoes 

 the moisture content is comparatively low, while the starch and 

 sugar are high; then comes a period of rapid growth, during which 

 the water increases and the starch and sugars decrease; and as the 

 potatoes approach maturity the tendency is for the starch to in- 

 crease and the total sugars and water to decrease. The relative 

 proportions of cane sugar and dextrose are shown to vary greatly, 

 dependent apparently upon meteorological conditions. The total 

 sugars during the periods of the tests varied between about 2 and 

 6 per cent. 



During the curing process and in storage physiological changes 

 take place which transform part of the starch to sugars and inter- 

 mediate products. These transformations have been followed care- 

 fulh^ by several investigators. Harrington (7) was the first in- 

 vestigator, apparently, to note these changes. In a study of 16 

 varieties, covering a period of a little more than four months, this 

 worker found that the average water content decreased from 71.35 

 to 63.5 per cent, the invert sugar increased from 3.17 to 4.63 per 

 cent, and the total sugars increased from 6.27 to 12.31 per cent. 

 Taking as the cane-sugar content the difference between the total 

 sugars and the invert sugar, it is found that the cane sugar increased 

 from 3.1 to 7.68 per cent during this period. Shiver {18) obtained 

 similar results, but noted a slight increase in the moisture content 

 during storage. He showed, however, that there may be either an 

 increase or a decrease in the moisture content, depending upon the 

 storage conditions. Hasselbring and Hawkins {8, 10) have studied 

 the chemical changes taking place when sweet potatoes are stored 

 at different temperatures. They find a very great decrease in the 

 starch and dextrose and a very great increase in the cane sugar when 

 the potatoes are stored at low temperatures. These authors {9) 

 have also measured the respiration of sweet potatoes during storage 

 and have found some loss in reducing sugars through this cause. 

 Miyaki {17), in studies upon the nature of the sugars found in 

 sweet potatoes, concluded that the reducing sugars consisted of both 



