What is the characteristic of the white of an USDA grade AA egg?

The characteristic of a USDA grade AA egg white being thick and firm indicates that it has a high quality and freshness. This quality level signifies that the egg has been stored properly and is relatively fresh, often having just been laid. The thick and firm nature of the egg white—known as the albumen—provides a stable structure that holds its shape well when the egg is cracked open. This is essential for cooking methods that require a stable protein structure, such as poaching or whipping for meringues. High-quality egg whites also contribute to better volume and texture in recipes, making them ideal for culinary applications.

In contrast, the other options describe characteristics that would be associated with lower grades of eggs or those that have been stored longer or improperly. Runny and thin whites indicate degradation of quality; pale and watery would also suggest age or mishandling. Lastly, while transparency is a sign of freshness to some extent, it does not directly correspond with the classification of the thickness and firmness that USDA grade AA eggs are known for.