What physical characteristic of eggs is considered in the USDA grading system?

In the USDA grading system for eggs, one of the most important physical characteristics considered is the size of the air cell. The air cell forms as the contents of the egg cool and contract after laying, creating a pocket of air that develops at the wide end of the egg. During grading, larger air cells typically indicate that the egg is older, as they increase in size over time due to moisture and air loss through the shell.

Grade AA eggs, for example, have small air cells, indicating their freshness, while Grade A eggs have slightly larger air cells, and Grade B eggs have even larger air cells, which affects their quality and usability in various culinary applications.

The other physical characteristics, such as shell color, shape, and texture, do not play a role in determining the grade of an egg. Instead, they may affect consumer preference but are not part of the USDA's grading criteria. Consequently, air cell size is the characteristic that directly influences the grading system's quality assessments.