26 BULLETIN 123, U. S. DEPARTMENT OF AGRICULTURE. 
Old and wrinkled potatoes are much improved by cutting off the 
ends or by partially or wholly paring and soaking in cold water for 
several hours. In fact, inferior potatoes of any age are much im- 
proved by paring and soaking. Where potatoes are inexpensive or 
the parings can be fed to animals, it is often a profitable custom to 
pare before cooking, since thus imperfections and strong-flavored 
portions are disposed of, leaving a nearly pure starch, comparable to 
arrowroot or tapioca and ready for the table as soon as cooked; this 
is true notwithstanding that careful investigations have proved that 
such cooking causes considerable loss of the nutrients in the potato. 
The way in which foods are cooked has some effect on their food 
value. In the case of potatoes it has been found that when boiled 
with the skins removed there is a very considerable loss not only of 
organic nutrients but also of mineral salts. (Fig. 3.) When boiled 
with the skins on, 
CABO ORITES 12496 fin 995 Exes the loss of nutrients 
ASH lO Lae FQ is very slight. In 
at the case of potatoes 
WATER FA 3% baked in the jackets, 
little if any nutritive 
| material is lost. Itis 
5 a self-evident that, if it 
Fic. 3.—Composition of the potato. The shaded portion is desired to cook po- 
represents the average loss of nutrients when boiled with tatoes with as little 
the skin on. 
loss as possible, they 
should be either boiled or baked with the skins on. When potatoes 
are the only vegetable obtainable it may be especially important 
to cook them without paring, so that their mineral salts may be re- 
tained, but people who use plants and other vegetables freely may 
be justified in considering chiefly convenience and palatability in the 
preparation of these tubers. 
Often it is a convenience for the housekeeper who has several dishes 
to prepare at once just before dinner to have the potatoes pared earlier 
in the day. Ifso, they should be put in water with a little salt added, 
so that they will not turn dark. 
Most good cooks believe that it is wiser-to discard the water in 
which potatoes are boiled, as it is likely to be strong in flavor, rather 
than to save it for soup making or for some similar use as is recom- 
mended for the water in which celery, etc., is cooked. (See Lesson IT.) 
Potato flour may be found in large groceries and is used in cakes 
and for thickening purposes. 
SWEET POTATOES. 
Sweet potatoes are not strictly tubers, but tuberous roots. There 
are many varieties, with different shape and color. Northern mar- 
