Final answer:
Overbeaten egg whites look dry and clumpy due to the breakdown of the foam structure formed by albumin. Unlike the irreversible denaturation of egg whites when cooked, overbeaten egg whites might be rectified by adding an unbeaten egg white.
Step-by-step explanation:
Overbeaten egg whites take on a dry, clumpy, and grainy appearance, contrasting with the glossy, smooth texture of properly beaten egg whites. When egg whites are beaten, albumin, the main protein, unfolds and forms a network that traps air, creating foam. If this process is continued for too long, the foam structure breaks down, and the whites become overbeaten, starting to separate into dry clumps which can ruin the intended texture of dishes they are used in like meringues or soufflés. The physical change from a clear liquid to a solid foam represents a form of denaturation, where the protein structure is altered, similar to when an egg is cooked, and the egg white turns from clear to opaque. Unlike the irreversible process of cooking where the albumin aggregates into a disorganized solid above 373 K, overbeaten egg whites can sometimes be salvaged by gently folding in an additional unbeaten egg white to re-introduce moisture and proteins that can help to re-form the foam structure.