Back in the day, the interior of eggs is inspected by using candlelight. Today, this inspection process is still called candling but through the use of high-intensity light. On July 20, 2020, the United States Department of Agriculture (USDA) had set specific guidelines when it comes to grading eggs. They were based on the standards set by the U.S.Standards for the Quality of individual Shell Eggs. Below are the different grades of consumer eggs, and their respective descriptions.
This is the highest quality of eggs you can buy. Their shells should be significantly clean, unbroken, and have the shape of traditional eggs. The space between the albumen (egg white) and the shell is called an air cell, which can be found at the larger end of an egg. Grade AA eggs should have an air cell of not be more than 1/8-inch in depth. The yolk should be centered, have a slightly defined outline, and has no defect. On the other hand, the white should be firm and clear.
The shell of Grade A eggs may be similar to that of Grade AA eggs. On the other hand, the air cell should not be more than 3/16-inch in depth. The yolk should also be relatively centered, have a fairly defined outline, and without defect, while the white should be reasonably clean and firm. Nevertheless, they may show some traces of processing oil.
Grade B eggs are also considered fresh but have the lowest quality among the three. They may have moderately stained areas but still acceptable if the stain is not more than 1/8 inch in diameter. For localized stain, it should not cover more than 1/32 of the shell surface. For scattered stain, it should not cover more than 1/16 of the shell surface. Nevertheless, adhering soil and prominent stains are not acceptable. The outline of the yolk should be visible, while the white should be clear but maybe watery and weak.
An egg can be classified as dirty or reject and is considered inedible although the shell is not broken. Based on the inspection, the localized stain is covering more than 1/32 of the shell surface or more than 1/16 of the shell surface if the stain is scattered. Likewise, the presence of moderate stain is more than 1/8 inch in diameter. The adhering dirt is also 1 mm wide or greater.
A “check” egg is considered as having lower quality than that of a dirty egg and is therefore also not suitable for human consumption. It has a broken shell, although the membranes are still intact and have no leak.
As the name implies, the shell of a “leaker” egg has a crack and the content tends to come out any time or is already exposed. For obvious reasons, it is no longer edible.