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mixed rot class, since all represent the first stages of yolk deterioration. The color before the candle of mixed and white rots, like that of fresh eggs, depends on the color of both the shell and the yolk. A light yellow yolk in a white shell, has a pale yellow appearance before the candle, and a brown shell or a dark yellow yolk in a white shell gives a reddish color. Brown shells or pale yolks in white shells are factors which reduce the contrast between white and yolk. The candler may very easily confuse the general yellow or pinkish color of good eggs with that of a mixed or white rot if he does not study the condition of the yolk and allow for the color of the shell. Even with close examination it may not be possible always to distinguish between a whole and a broken yolk. In some instances the entire yolk membrane may be so weak that the outline of the yolk changes when the egg is turned, making it difficult to determine whether it is whole or not. In other cases the presence of the yolk in the white, due to seepage, can not be detected because of the opacity of the shell. Again the white may be so firm that it tends to prevent the spreading of the yolk material, even though the yolk sac may be ruptured. These different forms of yolk deterioration are readily recognized when the egg is opened.

Table 2 shows that out of 187 cases of eggs 505 white rots and 450 mixed rots were found, of which 89.71 per cent and 67.12 per cent, respectively, were detected by commercial candling. The proportion of these eggs miscandled in refrigerator eggs was practically the same (Table 2). As white rots are an advanced form of mixed rots, and present more distinctive characteristics before the candle, it is to be expected that the error in candling would be less. The data given in Table 3 further confirm these findings.

EGGS WITH SLIGHTLY STUCK YOLKS.

The egg with the slightly stuck yolk, representing one of the most common types of deterioration in summer, is very frequently miscandled. A pale yolk or a brown shell increases the difficulty of detection. In addition, when the yolk is stuck by a small area only it may sway back and forth so readily that it is difficult to determine whether it is free or adherent. If the turning during the candling tears the yolk from the shell it may be so slightly broken and the white so firm that it is almost impossible to determine whether the yolk is whole or broken. The yellow stain on the shell marking the place where the yolk was stuck and which is characteristic of this egg when out of the shall is not always visible before the candle.

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Checking the decision made by candling with the appearance of egg out of the shell is one of the most effective means of becom

ing skilled in the grading of eggs with stuck yolks. When they are the prevailing type of bad eggs present judgment of grade should be made as far as possible with the first turning of the egg before the candle, because further rotation often serves to make detection more difficult. The distinguishing feature to be looked for is the adhering portion of the yolk.

In the lots of eggs reported in Table 2 from 40.57 to 78.70 per cent of the eggs with slightly adherent yolks were found by candling. In the summer breaking stock and refrigerator eggs it was the leading type of eggs miscandled (Tables 2 and 3).

BLOOD RINGS AND LARGE EMBRYOS.

Fertile eggs containing blood rings occur most frequently when the weather is sufficiently warm to cause development of the germ spots. In the early stages when there is but a mere trace of blood present, it is not always easy to find them by candling, especially if they happen to be inclosed in a brown shell. In the later stages when the yolk is weak, the blood ring may be covered with a fold in the yolk, and thus escape detection. The blood ring is best seen if the egg is turned gradually before the candle so that the yolk revolves slowly, allowing the germinal spot and the surrounding area which has a rosy appearance to float near the shell. When the yolk is near the shell a darkened area should be looked for, and, if this is present, it should be examined carefully for dark or red streaks or a ring. A candle with a bright light is absolutely necessary if small blood rings are to be found. When the blood-veined area has developed to the size of a 5-cent piece or larger its detection is ordinarily a simple matter.

The ease with which serious errors in failing to find blood-ring eggs may occur. was well illustrated in one house under observation where careless candlers working with dimly lighted candles put 3.4 per cent of such eggs into seconds intended to be edible. In the summer breaking stock as many blood rings as white rots were misgraded (Table 3). The use of a candle with a weak light or with an opening which is too large results in failure to detect these eggs.

EGGS WITH BLOODY WHITES.

Eggs with bloody whites are caused by the rupture of the blood. vessels during the passage of the egg down the oviduct. Their occurrence is comparatively rare, for out of 357.2 cases of eggs studied but 23 were found. Of these 7 were found by candling and the balance by breaking. These eggs are not readily seen in the shell because the pinkish tint due to the presence of blood is very nearly the same as that given by a brown shell or a white shell con58079°-18-Bull. 702-2

taining, a dark-yellow yolk. When blood clots are present, as is frequently the case, they serve to make identification easier. If eggs with diffused blood occurred more frequently, candlers would become more familiar with their characteristics, and a larger percentage would no doubt be recognized by candling.

BAD EGGS NOT DISTINGUISHABLE BY CANDLING.

EGGS WITH ABNORMAL ODORS.

Eggs with abnormal odors, including sour and musty eggs, constituted a large proportion of the inedible eggs which could not be detected by candling (Tables 2 and 3). The well-known musty egg in many instances presents an exceptionally fresh appearance before the candle and out of the shell. Only occasionally is the odor so strong that it can be noticed before the egg is opened.

The egg with the sour odor frequently shows such extensive physical deterioration that it can be recognized as a white or mixed rot on candling. If, however, disintegration has not progressed to such an extent, it can not be detected except by the sense of smell when the egg is broken. Bacteriological studies show that the characteristic odor is not produced until the bacteria have developed in large numbers.1 Eggs having ammoniacal or fishy odors due to bacterial deterioration are not uncommon, and, as in the case of sour eggs, physical changes may not be apparent until an enormous number of bacteria have accumulated. These, too, are identified by the abnormal or characteristic odor apparent when the eggshell is removed. Because their shells are porous, eggs absorb odors easily from surrounding materials. Very frequently eggs have the odor of moth balls, kerosene, carbolic acid, mold, and damp fillers and flats. Some of the absorbed odors disappear after the egg has been opened, but others remain permanently. Eggs which retain abnormal odors are rejected, and, since the odor is such an important factor in grading eggs out of the shell, great care must be exercised in grading when an odor is present.

EGGS WITH GREEN WHITES.

Eggs with green whites constituted a large proportion of the bad eggs not discernible by candling. They are recognized by the green color of the white when the egg is opened. This color is not present until the specific organisms which produce it have multiplied enormously. Because these eggs are so heavily infected and are chemically decomposed, care should be taken to eliminate them from food products.

1 U. S. Dept. Agr. Bul. 51, page 61.

EFFICIENCY OF CANDLING REJECTS.

Just as the bad eggs found in eggs candled as good were studied to determine the reason for their not being discovered, the good eggs found in eggs candled as bad were subjected to critical tests to find out why they were miscandled. In this work attention was directed more to the characteristic appearance before the candle, than to the condition found when breaking the egg out of the shell. The latter method was resorted to only when there was doubt concerning the quality of the egg as ascertained by candling.

To determine how many good eggs were placed with the bad eggs and what the characteristics of these eggs were, 12,024 rejected eggs, mostly from inexperienced candlers, were critically recandled. Among the bad eggs were found 19.9 per cent good eggs, divided between six main groups, namely, brown eggs, hatch-spot and weak eggs, eggs with the yolk floating near the shell, eggs with olive-green yolks, good eggs with broken air cells, and good eggs included because of carelessness (Table 4). As the causes of error for the six types of eggs are different, each will be discussed separately.

TABLE 4.-Kinds of good eggs in eggs candled as bad and doubtful (determined by recandling).

12,024 eggs (33.4 cases) candled as bad and doubtful.

[80.1 per cent bad eggs.

(6.3 per cent eggs with brown shells.

5.6 per cent heated eggs, including hatch-spot and weak eggs.

3.1 per cent eggs with the yolk floating near the shell.

19.9 per cent good eggs..2.1 per cent eggs with olive-green yolks.

1.4 per cent good eggs, probably due to carelessness. 1.2 per cent eggs with movable air cells.

0.2 per cent eggs with dirty shells, double yolks, and leakers.

GOOD EGGS IN REJECTS.

BROWN EGGS.

Brown eggs constituted about one-third of the good eggs not detected by candling (Table 4). The brown shell, in giving the egg a general reddish color before the candle, reduces the contrast between the white and yolk. This difference is due to a, lesser degree of transparency in the case of the eggs with brown shells. The darker the color of the shell, the more difficult it is to judge the condition of the contents. The bad eggs with which good eggs in brown shells may be confused are mainly mixed and white rots, eggs with slightly stuck yolks, blood rings, and eggs with blood in the whites. A candle with a bright light and with an opening of the proper size, so that no rays of light escape around the egg, is a prerequisite for the satisfactory grading of these eggs. With a little study and experience there should be small difficulty in detecting any except those with extremely dark shells. An egg with a stained shell is sometimes miscandled because the appearance before the

candle gives a false impression of the condition of the contents. The inspection of the egg without the aid of the candle is usually sufficient to correct this delusion.

HEATED EGGS INCLUDING HATCH-SPOT EGGS AND WEAK EGGS.

Weak eggs and hatch-spot eggs are characteristic of summer seconds. They formed over 5 per cent of the good eggs found in the rejects. The warmth of the summer weather enables the native enzymes to weaken the structure of the egg, and, if the egg happens to be fertile, a partial development of the embryo also occurs. Because the yolk of an egg with a weak vitelline membrane flattens out with each turn before the candle, it is not always easy to determine whether or not the yolk is intact. If the yolk besides being weak shows signs of incubation, it is necessary to determine whether blood is present. A dark shell or a white shell inclosing a lightcolored yolk also makes for inaccuracy. If new candlers are not instructed they invariably throw away hatch-spot eggs because of the darkened area on the yolk.

EGGS WITH YOLKS FLOATING NEAR SHELLS.

Eggs with the yolk floating near the shell are frequently mistaken for eggs with slightly adherent yolks, if the candler does not invert each egg to see whether the yolk will move away from the shell. It sometimes happens that the jar of placing an egg with a slightly stuck yolk in the case dislodges the yolk so that upon recandling it has the appearance of a good egg. About 3 per cent of the good eggs found on recandling rejects were eggs with yolks resting near the shell.

TABLE 5.-Accuracy of recandling rejects.

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