POTATOES AND OTHER STARCHY ROOTS AS FOOD. 
Table I. — Composition of raw and cooked potatoes. 
Kind of food. 
Refuse. 
Water. 
Protein, 
Fat. 
Carbohydrates. 
Ash. 
Sugar, 
starch, 
etc. 
Crude 
fiber. 
Per ct. 
Per ct. 
Per ct. 
13.8 
0.9 
0.8 
18.0 
.4 
1.0 
20.3 
.6 
1.0 
17.8 
1.5 
46.7 
4.5 
22.0 
1.0 
92.8 
82.3 | 1.8 
3.4 
80.9 
3.1 
52.6 
.5 
1.1 
Fuel 
value 
per 
pound. 
Potato, as purchased 
Potato, edible portion 
Potato, boiled 
Potato, mashed and seasoned 
Potatoes, fried in fat (potato chips) . 
Baked potatoes 
Potato starch (potato flour) 
Potato meal and flakes 
Potato, evaporated 
White bread, for comparison , 
Per ct. 
20.0 
Per ct. 
62.6 
78.3 
75.5 
75.1 
2.2 
74.0 
7.1 
7.6 
7.1 
35.3 
Per ct. 
1.8 
2.2 
2.5 
2.6 
6.8 
3.0 
.1 
4.6 
8.5 
9.2 
Per ct. 
0.1 
.1 
.1 
3.0 
.4 
L.3 
Calories. 
305 
375 
430 
490 
2,595 
455 
1,685 
1,620 
1, 610 
1,185 
As the table shows, the refuse, that is, the part removed in prepar- 
ing potatoes for eating either before they are cooked or at the table, 
makes up on an average about one-fifth of the whole tuber, and the 
part commonly eaten, that is, the edible portion, four-fifths. Water 
is the most abundant constituent of the potato and forms about three- 
fourths of the edible substance. The remainder is mostly starch, 
though there is a little nitrogenous matter (protein) and fat. The 
amount of mineral matter (ash) 
is actually small, but as compared 
with that in other foods it is rela- 
tively high, and is of much value 
in nutrition. Figure 3 represents 
in graphic form the composition 
of the edible portion of the po- 
tato and shows even more plainly 
than the table that the bulk of the 
potato tuber is water. 
Theoretically, the skin is the 
only refuse or inedible material in 
the potato, but in practice a con- 
siderable part of the edible por- 
tion is removed with it (fig. 4). 
When the surface is irregular, or 
the tubers have shriveled in storage, a much greater proportion of the 
flesh is likely to be cut off with the skin in paring than is the case when 
the tubers are smooth and in good condition. It is estimated that in 
paring raw potatoes by household methods the loss is about 20 
per cent. This includes not only all of the skin and the corti- 
cal layer, but also 9 per cent of the flesh. When we recall how large 
is the proportion of water and how low that of nutrients in the tuber, 
and also that the larger proportion of the protein and mineral mat- 
V^// /O/p 
Fig. 3. — Percentages and loss in digestion 
of nutrients of the potato. Shaded 
portion shows a loss in digestion of 15 
per cent of the protein and 1 per cent 
of the carbohydrates. 
