What Do Different Egg Grades Mean?

There's no shortage of labels on eggs these days — large, jumbo, free-range, organic, etc. But what's up with the grading system? And is it really necessary to purchase the highest grade eggs? It depends on how you plan to cook with them. Here we'll explore what makes one egg a Grade AA and one a Grade A (and sometimes, a Grade B).

What Is Egg Grading?

Egg grading is a voluntary service provided by the U.S. Department of Agriculture (USDA) and paid for by egg producers. It involves sorting eggs into one of three grades: Grade AA, Grade A, and Grade B. Each grade is determined by assessing the interior quality of the egg and the exterior quality of the egg shell. Eggs of the same grade can be different sizes (from Jumbo down to Peewee) or colors (brown or white).

How Are Eggs Graded?

Eggs are graded based on both their exterior and interior condition to help establish uniform standards for egg quality.

Exterior Quality

Turns out, eggs are very much judged by their covers: "It's more about appearance than anything," Serena Schaffner with the American Egg Board told me. The shells are inspected according to the following factors:

• Shell Shape and Texture: A normal egg should be oval in shape with one end larger than the other end and free of ridges or rough spots.
• Soundness of Shell: A sound egg is one whose shell is considered unbroken.
• Shell Cleanliness: A shell is considered clean if it is free of stains and discolorations. An egg with small specks or cage marks can still be considered clean.

Interior Quality

So, how do they inspect the interior of the eggs without breaking them? It can be done using an old-time technique called egg candling. You hold the egg up to a bright light in a dark room. At one time farmers used a candle, but now folks use an electronic egg candler. (Yes, you may buy one on Amazon.) Using this technique, eggs are graded according to the following factors:

• Air Cell: When the egg is first laid, it has very little air inside, or none at all. As its temperature cools, the liquid contracts and the inner shell membrane separates from the outer to form what's known as an air cell. The smaller the depth of the air cell, the higher the grade.
• Yolk and White: When holding the egg up to a light, you want a yolk outline that is only slightly defined, as this indicates a thicker white and a yolk that is not off-color. The interior is also checked for blood spots or other blemishes.

Consumer Egg Grades

Grade AA and A eggs are most commonly found in supermarkets, while Grade B eggs are often used to make liquid, frozen, or dried egg products.

USDA Grade AA

The highest grade is AA. These eggs must have clean, unbroken shells that are normal in shape. Grade AA eggs' air cells must not exceed 1/8-inch in depth. Their white must be clear and firm and their yolk must be only slightly defined when twirled before a light. And of course, the yolk must be practically free of any apparent defects.

USDA Grade A

Like Grade AA, Grade A eggs must have clean, unbroken shells of normal shape. The air cell of a Grade A egg must not exceed 3/16-inch in depth. The whites should be clear and reasonably firm, so that the yolk is only fairly well defined. Finally, it must be practically free of any apparent defects.

USDA Grade B

Though safe to eat, Grade B eggs aren't often found in supermarkets. They don't meet the same standard as Grade AA and Grade A eggs, which is why they're often saved for use in liquid, frozen, or dried egg products.

A Grade B egg must have an unbroken shell, but it can be abnormal in shape and slightly stained. The air cell may be over 3/16-inch in depth, the white may be weak and watery, and the yolk outline may be distinct, dark, enlarged, and flattened. Small blood spots may be present, but it should have no serious defects.

What Grade Eggs Should You Use for Cooking or Baking?

The USDA has a 50-page manual on egg grading. But the basic facts are these:

• Use Grade AA when you're preparing an egg dish in which the egg's appearance is important, such as fried eggs.
• Use Grade A or Grade B if you're mixing the eggs into the dish or using them to bake, as the difference is largely in appearances and they're still perfectly safe to consume.

Related:

• All About Eggs: Grades, Safety, Nutrition & More
• How To Tell If Your Eggs Are Bad
• Are Eggs Actually Bad for Your Cholesterol?