by Nefer

BLOOD SPOTS:

These are also called meat spots. Have you ever found an egg yolk with a tiny blood spot?  Contrary to popular belief, these tiny spots do not indicate a fertilized egg.  They are caused by the rupture of a blood vessel on the yolk surface during the formation of the egg or by a similar accident in the wall of the oviduct. As the hen develops and ages, you may notice this occurance as it is quite common.

Mass candling methods in the commercial industry are able to reveal most eggs with blood spots.   Those eggs are removed but, even with electronic spotters, it is impossible to catch all of them. As an egg ages, from the moment it is laid, the yolk takes up water from the albumen to dilute the blood spot. It may still be there but invisible to the naked eye.  Actually a blood spot indicates that the egg is fresh. Both chemically and nutritionally, these eggs are edible. Removal is often suggested.

SHELL COLOR:

Many believe that shell color reveals the nutritional value of an egg, but it has no affect on nutrition. Egg shell color is determined by the breed from which it is layed. Yolk color may vary, depending upon age of the egg and the nutrition hen is receiving. The color comes from pigments in the outer layer of the shell and may range in various breeds from white to deep brown. Those breeds are known for laying the rainbow of colors from pinks to greens. In most cases, your red earlobed breeds will lay a brown egg. White earlobed breeds tend to lay white eggs. Shell color can be lost due to calcium deficiencies and age. These factors can also influence a shell's texture and thickness.

The strength of the shell is dependent on the minerals and vitamins in the hen's diet, particularly calcium, phosphorus, manganese and Vitamin D.  If the diet is deficient in calcium, for example, the hen will produce a thin or soft-shelled egg or possibly an egg with no shell at all. Occasionally an egg may be prematurely expelled from the uterus due to injury or excitement. In this case, the shell has not had time to form completely. Shell thickness is also related to egg size and the age of the hen.  As the hen ages, the size of the egg will increase.  This can be very noticeable in the bantam breeds. The shell is covered with a protective coating called the cuticle or bloom.  By blocking the pores, the cuticle helps to preserve freshness and prevent microbial contamination of the contents. This is why it is important to only remove dirt and debis with water or a damp cloth so you will not damage the thin protective coating.

YOLK:

The yolk or yellow portion of an egg makes up about 33% of the liquid weight.  Nutrition can greatly influence the color and flavor of a yolk. Hens receiving a diet high in roughage and folliage, such as lettuce, grasses, plant folliage or alfalfa will have a yolk rich in appearance; ranging from a deep yellow to orange. As moisture is lost through the shell of the egg, the yolk may also lose its firmness upon breakage.

Double-yolked eggs may be produced by young hens whose egg production cycles are not yet completely synchronized. A disturbance in the cycle can also produce the release of two yolks. Occasionally a hen will produce double-yolked eggs throughout her egg-laying career. It is rare, but not unusual, for a young hen to produce an egg with no yolk at all. This may be due to immaturity or a disturbance in the cycle. There have been records revealing an egg to have contained 3 to 5 yolks. 

THE WHITE:

There are several signs determining freshness in the egg and the egg white.  Does the egg hold it shape or appear flat; is the white of the egg runny or stiff? Egg albumen in raw eggs is opalescent and does not appear white until it is beaten or cooked. A yellow or greenish cast in a raw white egg may indicate the presence of riboflavin. Cloudiness is due to the presence of carbon dioxide which has not had time to escape through the shell and thus indicates a very fresh egg. Runny or watery whites signify an egg that is old or has been held to long. As the egg ages, carbon dioxide escapes, so the albumen of older eggs is more transparent than that of fresher eggs. This process begins the minute an egg is layed.


CHALAZA:

These are stringy strands of egg white which anchor the yolk in place in the center of the thick white. They are neither imperfections nor beginning embryos.


THE DEVELOPMENT OF THE EGG

Chickens have what is known as an "open" pelvis. The symfysis are not closed and allows enough room for the egg to come through.

The egg begins as a yolk which "falls" from the ovary into a kind of funnel.  This is the place of impregnation.

Step 1: Thickening of the yolk-skin (15 min.)

Step 2: White-of-egg forming part from the tube (3 hours), half part of the white-of-egg is made in here and also the strains on which the yolk is hanging.

Step 3: Yolk-skin forming part, again 10% white-of-egg forming and both the egg-skins (11/2-2 hours).

Step 4: Production of the egg-shell, before this takes place another 40% white-of-egg is made.

Step 5: In the tube, the coloring of the egg-shell is made and also the protective egg-skin. The making of the egg-shell takes about 20-21 hours.

Finally the egg is pushed outside.  It takes about 25 hours for an egg to be made.

(Parts of an Egg by the USDA)
Handbook # 75 

Diagram provided by; Mama Tami

"The parts of an Egg provided by Mama Tami"
for educational purposes only

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FERTILE EGGS:

Eggs which can be incubated and developed into chicks are called fertile eggs.  Fertile eggs are not more nutritious than nonfertile eggs.  They do not keep as well as nonfertile eggs and are more expensive to produce.  This cose is passed on to the consumer.


FRESHNESS OF THE EGG:

From the moment an egg is laid it is subject to the environment. This has a bearing on its freshness but is only one of many factors. The temperature at which it is held, the humidity and the handling all will play a part. These variables are so important that an egg one week old, held under ideal conditions, can be fresher than an egg left at room temperature for one day. The ideal conditions are temperatures that do not go above 40°F. (4°C.) and a relative humidity of 70 to 80%. Proper handling means prompt gathering and removing debis to proper storage. As an egg ages, the white becomes thinner and the yolk becomes flatter. These changes do not have any great effect on the nutritional value of the egg.


SIZE:

Several factors influence the size of an egg. The major factor is the age of the hen.  As the hen ages, her eggs increase in size. The breed of hen laying the egg is a second factor.  As far as nutritional value, size does not have any influence. In the grading of eggs, one of the things considered is weight.  Egg sizes are jumbo, extra large, large, medium and small with weights being considered. Weight is expressed in ounces per dozen. Eggs that are sold should be free of blemishes or debris. The texture should be smooth and uniform in shape. it is important to store eggs in their carton because eggs can absorb refrigerator odors.  This will also protect the egg from cracks that can lead to bacteria exposure.