22 BULLETIN" 784, U. S. DEPARTMENT OE AGRICULTURE. 
Sources of information. — Farmers' Bulletin 295 ; Office of the Secre- 
tary Circular 106: Department Bulletin 468; bulletins from State 
college of agriculture. 
Illustrative material. — Construct a chart showing the composition 
of the potato; another showing the food value of the potato when 
compared with other foods. Samples of potato starch, alcohol, 
potato flour, and other products obtained from the potato. 
Class exercises. — The following topics are suggested for attention 
in this lesson : 
1. Composition of the potato — Water, starch, protein, crude fiber, 
fat, ash. Use iodin test for starch ; use nitric acid and ammonia test 
for protein. Put a bit of potato on a piece of paper and put it into 
the oven or on top of a stove which is not hot enough to burn the 
paper. After heating hold paper up to light and see whether you 
can note any evidence of fat. 
2. Uses of the potato — Potato starch, industrial alcohol, potato 
flour, glucose, sirup, mucilage, stock feed, and human food. Study 
briefly the minor uses mentioned above and the methods of making 
the products. Primarily, the chief attention should be given to the 
use of the potato as a human food. 
3. The potato as a human food — (a) Food values, chiefly a 
starch food, but contains some protein and mineral matter. 
(b) Advantages as a food — Furnishes an abundant supply of 
nutrients at a relatively low price: supplies nutrients in an easily 
digestible form ; adds bulk to the food eaten. 
(c) Textures of flesh in cooked potato — Soggy, usually rather low 
in starch and relatively high in protein ; waxy, a greater proportion of 
starch to protein : mealy, starch content high, protein relatively low. 
(d) Place in the general diet — Potatoes represent 3.9 per cent of 
the total cost of food, furnish 5.3 per cent of the total calories, 4.2 per 
cent of the total protein, 8.7 per cent of the total phosphorus, and 
13.5 per cent of the total iron. Since phosphorus and iron com- 
pounds are as import-ant to include in the dietary as protein and fuel 
foods, it is seen that for the small percentage of money expended for 
potatoes a generous supply of nutrients is obtained. 
(e) Cooking — (1) Effects of cooking: transforms water into 
steam, expanding breaks down starch cells and free starch grains, 
coagulates the protein, affects minerals only slightly. Baking and 
steaming from all points of view are the best methods of cooking 
potatoes. (2) Losses in cooking; in paring, both by cutting away 
valuable material and exposing the soluble substances to the action of 
the water: in exposing a large amount of surface to the water: in 
soaking before cooking : in the use of cold water at the beginning of 
the cooking. (3) Recipes for using potatoes. Here a number of 
