The perfect fried egg may be subjective, but the standard is a white free of bubbles, crispy bits, and browned portions surrounding an unbroken yolk that’s thickened but not hard.

When frying an egg, one should aim to hit the ideal texture and doneness of the white and yolk at once. The science behind that synchronization comes down to protein coagulation.

According to the Egg Safety Center, an egg white coagulates at 144 to 149 degrees Fahrenheit, while the yolk coagulates at 149 to 158 degrees Fahrenheit.

Egg whites, having more protein and higher water content than the yolks, cook faster. Hence, frying a cold egg exacerbates the problem that the white sets faster than the yolk.

A cold egg white can steam when cracked into a hot pan, cooking even more rapidly than usual without leaving the yolk enough time to set to its ideal doneness.

While frying eggs on low-medium heat can help, chef Robert Irvine advises allowing eggs to reach room temperature before cooking to keep the pan’s temperature from dropping.