POTATOES AND OTHER STARCHY ROOTS AS FOOD. 
27 
COMPOSITION AND ENERGY VALUE OF TROPICAL STARCHY ROOTS AS COMPARED 
WITH POTATOES AND SWEET POTATOES. 
Table III shows the composition of the tropical starchy roots as 
compared with potatoes and sweet potatoes. 
Table III. — Average composition of edible portion of dasheen and other tropical 
starch-bearing roots. 
Water. 
Protein. 
Fat. 
Total carbohy- 
drates. 
Ash. 
Fuel 
Kind of food. 
Sugar, 
starch, 
etc. 
Crude 
fiber. 
value per 
pound. 
Per ct. 
66.0 
10.5 
10.5 
10.3 
72.9 
65.7 
70.9 
70.0 
Per ct. 
1.1 
.5 
9.1 
1.1 
1.8 
3.0 
1.8 
2.2 
2.2 
1.8 
Per ct. 
0.2 
.1 
.3 
.2 
.2 
.2 
.2 
.2 
.1 
.7 
Per ct. 
30.2 
Per ct. 
1.8 
Per ct. 
0.7 
.1 
1.1 
1.6 
.9 
1.3 
1.2 
.9 
1.0 
1.1 
Calories. 
610 
88.8 
79.0 
1,625 
1,610 
1,605 
85.2 
23.3 
28.8 
23.2 
26.1 
18.0 
26.1 
1.6 
.6 
.7 
.8 
• .6 
.4 
1.3 
475 
605 
Taro 
475 
530 
78.3 
69.0 
380 
Sweet potatoes for comparison. . . . 
560 
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The preceding diagram (fig. 6) shows in graphic form the com 
position of sweet potatoes, Irish potatoes, 
and other starchy roots, and perhaps 
makes clearer data such as are recorded 
in the table. 
It is apparent from the diagram that 
these typical starchy roots are very simi- 
lar in general composition. Degree of 
ripeness, length of storage, and other fac- 
tors influence water content considerably. 
Individual specimens of any one of them 
would vary more or less in water content, 
but on the average water makes up about 
two-thirds to three-fourths of the total, 
while carbohydrates constitute the greater 
part of the nutritive material. These 
vary in the different groups, starch being 
the characteristic carbohydrate of pota- 
toes, cassava, and dasheen; sugar and 
starch of sweet potatoes; and inulin, lev- 
ulin, and pectose bodies of Jerusalem 
artichokes. The proportion of protein in 
these roots is small, but valuable in nutri- 
tion, in part because of the vitamins 
believed to accompany the nitrogenous 
material. The proportion of ash is actually small, though relatively 
large as compared with other foods. As a group, starchy roots are a 
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Fig. 7. — Energy value of some 
common starchy vegetables. 
