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EGGS

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Fig. 9. — Distribution of chickens in the United States according to the census of 1900. Reproduced by permission from

Taylor's Prices of Farm Products (Bulletin 209 of the Wisconsin Agricultural Experiment Station).

surplus production does not continue throughout the year, but only during those months which are most favorable to laying. From Tennessee and Kentucky most eggs are sent to market during the period from December to April; from southern Ohio, southern Kansas, Missouri, and Texas many eggs are shipped during March and April; in the later spring northern Kansas, Iowa, Illinois, and the Central States generally show their heaviest production, while for Michigan and Minnesota the season is still later.

For the country as a whole as judged by the data of the large markets, the months of March, April, May, and June are those in which the largest number of eggs are shipped by the producers. During these months many eggs are placed in cold storage to be sold later when the supply is less abundant and the price higher.

Eggs are graded in the market chiefly according to freshness, cleanliness, size, cracks, and color. Freshness in this connection means the firmness and state of preservation of the egg rather than the mere length of time since laying. This freshness is determined chiefly by the process known as candling, which consists in looking through the egg against a bright light, such as an incandescent electric light, surrounded by an opaque shield in which is a hole shaped like an egg but slightly smaller in size. The egg is pressed firmly against this hole, and as the light shines through it, the white and the air-chamber may be observed. Figure 10 shows the appearance of a fresh, sound egg and of eggs which have undergone different types of deterioration.

Eggs sufficiently sound to pass the candling test may still be subdivided into many grades according to age, color, size, and cleanliness. It is these qualities rather than chemical composition and nutritive value which determine the very different prices at which eggs are sold in the same market and at the same

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Fig. 10. — Appearance of different grades of eggs before the candle. A, fresh egg; B, shrunken (old) egg; C, “spot" egg (fungous growth); D, rotten egg.

Chemical Composition Since the price of eggs is determined entirely by considerations other than chemical composition, and eggs are never produced primarily for industrial uses in which the components are separated from each other, there has been no economic reason for the study of the causes and extent of variations in composition, and our information on these points is very meager as compared, for example, with the corresponding data for milk. Differences in composition seem usually due to different proportions of white and yolk. According to Langworthy the proportion of yolk (and therefore of fat) is greatest in the eggs of those breeds which are best adapted to fattening. Other things being alike the edible portion of white-shelled and dark-shelled eggs shows essentially the same composition and nutritive value.

The average composition of eggs of different kinds, as given by Langworthy, is shown in Table 12, the fuel values being recalculated by the use of the now accepted factors.

The figures given for hens' eggs in this table are the average of 60 American analyses compiled by Atwater and Bryant, in which the protein varied from 11.6 to 16.0 per cent and the fat from 8.6 to 15.1 per cent. The estimated averages of European writers fall well within these limits, but are apt to be somewhat higher in fat than the American average as given above. Thus the estimate of König, which is widely quoted, allows 12.55 per cent protein and 12.11 per cent fat.

Speaking in round numbers, we may say that the edible portion of the egg contains 72 to 75 per cent of water, about i per cent of ash, 12 to 14 per cent protein, 10 to 12 per cent fat; or about three fourths water, one eighth protein, and one eighth fat. Of the edible portion the yolk constitutes (by weight) a little over one third and the white a little under two thirds; and these are of very different composition. The white is about

1 United States Department of Agriculture, Oflice of Experiment Stations, Bulletin 28.

TABLE 12. AVERAGE COMPOSITION OF EGGS (LANGWORTHY)

DESCRIPTION

REFUSE

WATER PROTEIN (SHELL)

FAT | Ash

FUEL VALUE

PER POUND

Per cent Percen! Per cent Percent per cent Calories

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Hen:

Whole egg as purchased
Whole egg, edible portion .
White . . . . . . . .
Yolk . . . . . . . .
White-shelled eggs as pur!

chased . . . . . . Brown-shelled eggs as pur

chased . . . . . . . Duck:

Whole egg as purchased . . ]
Whole egg, edible portion.
White . . . . . . .

Yolk . . . . . . . .
Goose :

Whole egg as purchased
Whole egg, edible portion
White . . . . . .

Yolk . . . . . . .
Turkey :

Whole egg as purchased
Whole egg, edible portion .
White . . . . . .

Yolk . . . . . . . .
Guinea fowl:

Whole egg as purchased
Whole egg, edible portion.
White · · · · · ·

Yolk . . . . . . .
Plover:

Whole egg as purchased Whole egg, edible portion . Fresh-water turtle eggs . . Sea-turtle eggs . . . . . Salted duck eggs · · · ·

59.7 | 12.9
69.5 13.8

11.6
44.1 17.3

86.3

12.3
14.4

0.02
36.2

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618 700 210 1660

48.3

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