Imágenes de páginas
PDF
EPUB

1. Potatoes are put in the boxes and covered as soon

as dug, thus preventing them from heating in

the sun. 2. They are easily and quickly loaded on a wagon,

saving time. 3. They are convenient packages in which to carry

early potatoes to the home market. 4. The potatoes may be left at the store in the box and

delivered in the box when sold, saving handling

and bruising. 5. When drawing the main crop to the storage-cellar

they are convenient to handle. 6. They may be used for storing seed potatoes, apples,

etc., and carrying seed potatoes to the field to be planted.

CHAPTER XV CHEMICAL COMPOSITION AND FEEDING VALUE

Composition.—Early attempts were made to determine the food value of the potato by means of chemical analyses. In 1795 Pearson reported “Experiments and observations on the constituent parts of the potato root.” Einhof published analyses of the potato in 1805, as did Vanquelin in 1817. Rather more than fifty years ago Emmons in this country reported analyses. Lawes and Gilbert devoted considerable time to the study of the composition of potatoes, and more recently various agricultural experiment stations, notably the Connecticut State and the Minnesota Agricultural Experiment Stations, the Division of Chemistry, U. S. D. A., and various European institutions have been investigating the problem. The approximate chemical composition of a number of varieties is : Water, 75 per cent.; protein, 2.50 per cent.; ether extract, .08 per cent.; starch, 19.87 per cent.; fibre, •33 per cent.; other non-nitrogenous materials, .77 per cent.; ash, i per cent. A more extended analysis is taken from the Vermont Experiment Station, report 1901:

TABLE XII

[blocks in formation]
[blocks in formation]

2.28

0.36

0.06

1.26

0.68

The percentage of water usually ranges between 70 and 80 per cent., the extremes being 65 and 85 per cent. Potatoes contain more dry matter than any root crop.

Per cent.
White turnips . . . . . . . . . . 7 to 9
Rutabagas · · · · · · · · · · ·

9 to 14
Mangel-wurzels . . . . . . . . . 9 to 16
Sugar-beets . . . . . . . . . . . 12 to 24
Carrots . . . . . . . . . . . . 10 to 17
Parsnips . . . . . . . . . . . . 10 to 18
Potatoes . . . . . . . . . . . 20 to 30

.

.

.

.

About 85 per cent. of the matter is present in the solid portion, or marc, and 15 per cent. in the juice. It has been believed by many that the specific gravity of the tubers varied with the percentage of dry matter, and on this basis tables for ascertaining the dry matter present in the tubers from the specific gravity have been worked out and used considerably. From these data the starch content was determined. Woods,' of Maine, and Watson,’ of Virginia, found that the ratio existing between the specific gravity and the starch content is not fixed.

Starch is the most important constituent of the dry matter of potatoes; it generally constitutes 15 to 20 per cent. of the fresh tubers, but may be as low as 10 or as high as 25 per cent. Maine-grown potatoes are usually lower in their starch content than Europeangrown potatoes. The starch content varies with the variety and the locality. Northern-grown samples of the same variety usually contain more starch than Southern-grown samples."

2 Va. Bul. 55, p. 102; Bul. 56, p. 144.

1 Me. Bul. 57, p. 150. 3 Va. Bul. 56, p. 144.

[blocks in formation]

The above data show that potatoes are almost wholly digestible.

Feeding Value.—When abundant and low in price, potatoes may be fed to all classes of stock. In France, Girard fed 55 to 66 pounds of cooked potatoes per day to fattening steers and 472 to 672 pounds to sheep. Von Funke' found uncooked potatoes were good for all stock except pigs. He fed 60 pounds of raw potatoes, 6 pounds of linseed meal, and 9 pounds of clover hay, with salt, per 1,000 pounds, live weight, per day to fattening steers. . For milch cows, 25 pounds daily per 1,000 pounds, live weight, is the limit. For yearlings, ewes, and wether sheep, 25 pounds per 1,000 pounds, live weight, per day is advised, and fattening sheep, 40 pounds. For horses, about 12 pounds per 1,000 pounds, live weight, may be given with other food. Stock should not be watered soon after feeding potatoes, but preferably about half an hour before feeding. Potatoes are not a valuable food for young animals,

1 Snyder, Minn. Bul. 42, pp. 89, 90. 3 E. S. R., V., p. 812.

? Kellner, et al. E.S. R., XIV., P. 595. 4 Minn, Bul. 42, p. 95.

as they are deficient in protein and ash-hence, should not be fed to growing cattle under two years old, lambs, or young pigs, unless in very small amounts, with other food to balance the ration. At Wisconsin Experiment Station,' hogs ate cooked potatoes better than uncooked, and 445 pounds of cooked potatoes were equal to 100 pounds of corn-meal in feeding value. One pound of dry matter of corn is superior to one pound of dry matter of potatoes for making gains with pigs.

Cooking.— In cooking potatoes a considerable portion of the albumen may be lost. Peeled potatoes started in cold water lost 80 per cent. of albumen, while those started in hot water lost but 10 per cent. Less is lost if the potatoes are not peeled. Salt should be added to potatoes, because the mineral matter they contain is deficient in sodium salts, which are requisite for the human system, and because salt increases the palatability. Varieties vary in the time they require to cook, and even soil and climatic conditions have an influence. In a floury, mealy potato the starch grains have swollen and burst, and ruptured the cell-walls surrounding them, while in a soggy potato this has not taken place. Potatoes showing second growth will not cook uniformly; the last-grown portion will cook first. When second growth takes place the starch passes from the older portion to the new; hence, when cooked, the older portion appears to be hard and dark, while the newer portion is white and floury, the difference being due to the presence or absence of starch.

1 Wis. 'Seventh Annual Report, 1890, and Henry, “Feeds and Feeding,” p. 212.

« AnteriorContinuar »