POTATOES AND OTHER STARCHY ROOTS AS POOD. 

 Table I. — Composition of raw and cooked potatoes. 



Kind of food. 



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 , 



Refuse. 



Per ct. 

 20.0 



Water. 



Per ct. 



62.6 



78.3 



75.5 



75.1 



2.2 



74.0 



7.1 



7.6 



7.1 



35.3 



Protein. 



Per ct. 

 1.8 



2.2 

 2.5 

 2.6 

 6.8 

 3.0 

 .1 

 4.6 

 8.5 

 9.2 



Fat. 



Per ct. 



0.1 



.1 



.1 



3.0 



39.8 



.3 



.4 



1.3 



Carbohydrates. 



Sugar, 



starch, 



etc. 



Crude 

 fiber. 



Per ct. 



13.8 



18.0 



20.3 

 17.8 

 46.7 

 22.0 

 92.8 



82.3 | 

 80.9 



52.6 I 



Per ct. 



0.9 



.4 



Ash. 



Per ct. 

 0.8 

 1.0 

 1.0 

 1.5 

 4.5 

 1.0 



3.4 

 3.1 

 1.1 



Fuel 



value 



per 



pound. 



Calories. 



305 



375 



430 



490 



2,595 



455 



1,685 



1,620 



1,640 



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- 



#?// /.oj4 



Pig. 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. 



