EXTENSION COURSE IN VEGETABLE FOODS. 29 
cookery shows that potato, arrowroot, and probably tapioca and sago 
starch pastes are not made more easily digestible by long-continued 
cooking. However, in the case of starch still inclosed in cellulose 
cells, as in many starchy foods, the long-continued cooking may be 
necessary. (Fig. 4.) 
The selection of potato starch instead of corn or wheat starch for 
thickening sauces in accordance with the custom of French cooks 
is rational, since it does not require such long boiling for improvement 
in flavor as is the case with cornstarch. 
EXERCISES, LESSON V. 
Materials needed.—A potato for each student; any other tubers available; 
rice, tapioca, cornstarch, rice flour, fruit juice or jelly, milk, butter, salad 
dressing ; fancy cutters, slicer, and scoops; different styles of potato mashers 
and ricers. The latter are for trial; a fork may be used to mash a small 
quantity. 
Fic. 4.—Changes of starch cells in cooking: a, cells of a raw potato with starch grains in 
natural condition ; b, cells of a partially cooked potato; c, cells of a thoroughly boiled 
potato. 
Ezercises.—Let each student prepare a potato, each in slightly different 
fashion according to the directions given below; weigh before and after cook- 
ing, weigh refuse, estimate percentage of loss and the time and fuel required 
for cooking one potato. Are these factors proportionately increased for a 
larger quantity? Compare time required to pare potatoes before cooking and 
after. What advantages for either method? 
POTATOES. 
While the potatoes are cooking grate one raw potato, press out the water 
through a cloth or wire strainer into a glass measuring cup. Estimate per- 
centage of water in the potato, then wash out the starch in the strainer, add 
to that settled from the juice, and cook it. Observe the nature of the material 
remaining in the strainer. 
Among the methods of cooking potatoes which may be tried in this lesson are 
these: 
Baked (1): Serve one at the right moment, leave another until the moisture 
condenses and the potato becomes soggy, with unpleasant odor and flavor. 
Baked (2): Cut in two lengthwise, remove contents, mash, season, and 
return to skin. Add beaten egg white to one half, bake and notice difference, 
How is this difference caused? 
