Incubation and Embryology - University of Illinois

Some Consumer Concerns About Eggs

Consumers raise many questions about eggs. A need exists to erase doubts and eliminate incorrect information.


Perhaps the greatest doubt is that eggs should be avoided because they contribute to blood cholesterol and aggravate heart problems. The presence or absence of eggs in the ordinary American diet is not likely to greatly affect the level of blood cholesterol.

Various factors, dietary and otherwise, affect the level of cholesterol in the blood stream. Only a small minority of the population needs to avoid high-cholesterol foods. And they are the persons with high blood lipids who cannot utilize food cholesterol. Their conditions can be detected by tests.

Many people, including most of those with heart conditions, should be eating more nutritious foods such as eggs. Leading researchers have indicated that the high-quality protein found in eggs is needed by heart patients when rebuilding damaged heart muscle.


Some people say eggs have too much "speed" from chemicals added to the feed. No scientific facts substantiate this claim. Only approved additives can be used. Moreover, extensive monitoring for harmful residues is done.


Contrary to the beliefs of many critics, "organic eggs" do not have higher nutritional values. The chief characteristic of organic eggs may be a strong flavor acquired when the chickens eat bugs, worms, decaying matter, or similar materials. That is not a nutritional plus.

Animal fat

Eggs do not have too much animal fat causing them to be nutritionally undesirable as some people think. Rather, the fats in eggs are more like vegetable fats and are primarily unsaturated.

Shell color

Some users prefer brown eggs to white, or vice versa. They claim better flavor and nutrition. The only difference is in the color of the shell itself, which is determined by the breed of hen. If hens have been fed the same type of ration, their eggs will be nutritionally equivalent, regardless of shell color. The eggs will also have the same flavor-keeping quality, and whipping and cooking characteristics.

Fertile eggs

There is no scientific evidence that fertile eggs are nutritionally superior to infertile ones. Fertile eggs have remnants of the male's sperm and a small layer of cells that could form the embryo. The proportion of these to the total egg is so small that it is impossible to detect chemical differences between fertile and infertile eggs.

Pale yolks

Yolk color varies. It is almost completely dependent upon the feed the hen eats. Birds that have access to green plants or have yellow corn or alfalfa in their feed tend to produce dark yolks. Since commercial laying hens are confined, lighter and more uniformly colored yolks are being produced. Yolk color does not affect nutritive value or cooking characteristics. Egg yolks are a rich source of vitamin A regardless of color.

Green whites

Greenish color in egg whites is usually due to riboflavin (vitamin B2), that is a desirable component. So there is nothing wrong with greenish whites that are most frequently observed in fresh, high-quality eggs.

Cloudy whites

This condition is noticeable in freshly laid or oil-treated fresh eggs. It is caused by the naturally occurring carbon dioxide. As the egg ages and this gas escapes, the white becomes clearer. The quality and flavor of eggs with cloudy whites is excellent.


Consumers frequently ask about the stringy white pieces in egg whites. Some think they are evidence of fertileness and very carefully remove them. They are, of course, a natural part of the egg and anchor the yolk in the thick white. Prominent chalazae indicate high quality. They tend to disappear as the quality of the egg drops. However, eggs with small chalazae can have high quality, too.

Difficult peeling

Hard-cooked eggs that do not peel easily are usually quite fresh. Eggs kept for several days before cooking lose carbon dioxide making them easier to peel.

Discolored yolks

The greenish coating around the yolks of hard-cooked eggs results from cooking at too high a temperature or too long a time or from not cooling the eggs rapidly following cooking. The sulfur and iron compounds formed at the surface of the yolk do not affect flavor or wholesomeness, although the greenish color is unattractive.

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