Why do egg whites turn white when you cook them?

January 17, 2019 by Matt Shipman, North Carolina State University
Credit: CC0 Public Domain

When you crack open a raw egg, the egg white isn't white at all—it's more like a clear jelly. So why does it turn white when you cook it? Does that make it safe to eat? And what about egg yolks?

What's in an egg white?

Egg whites, or albumen, are made up mostly of water. But they also contain dozens of different proteins, such as albumins. Those proteins are what make an egg white turn white when it's cooked.

Why do egg whites turn white?

"The short answer is that egg whites turn white because a chemical reaction takes place when the proteins in an egg white heat up," says Ben Chapman, a researcher at NC State University.

The long answer is a little more complicated.

When egg whites are raw, the proteins are curled up into tight balls, more or less floating in water. When heat is applied, those proteins uncoil and get tangled together. These tangled proteins form a kind of mesh, which traps the surrounding water. This changes the color and the physical consistency of the egg white.

How hot do egg whites need to be to turn white?

"Egg whites will start to get cloudy at approximately 140 degrees Fahrenheit, or 60 degrees Celsius," Chapman says. "At 149 degrees Fahrenheit (65C), the egg white becomes opaque, preventing light from passing through. This same process is what turns the egg white from a liquid into a solid."

Are egg whites safe to eat as soon as they turn white?

Pretty much.

"Cooking egg whites to 145 degrees Fahrenheit, or around 63 degrees Celsius, addresses pathogen risks—specifically the risks associated with Salmonella Enteritidis," says Natalie Seymour, a food safety expert at NC State. "And since egg whites set, or become solid, at 149 degrees Fahrenheit, that means they're safe to eat."

Are egg yolks safe to eat if they're still runny?

Maybe. It depends on how runny you're talking about.

"For food safety, egg yolks also have to be cooked to 145 degrees Fahrenheit," Seymour says. "That's still pretty runny. Egg yolks don't set until they reach 158 degrees Fahrenheit (70C). So, at 145 , egg yolks are still semiliquid, with a velvety texture."

Explore further: Rapidly cooling eggs can double shelf life, decrease risk of illness

Related Stories

A better way to pasteurize eggs

April 25, 2017

An Agricultural Research Service (ARS) scientist in Pennsylvania and his colleagues have developed a technology that rapidly pasteurizes eggs and could sharply reduce the number of illnesses caused each year by egg-borne ...

Whites have longest survival in cutaneous melanoma

October 29, 2016

(HealthDay)—For patients with cutaneous melanoma, whites have the longest survival time, according to a study published in the November issue of the Journal of the American Academy of Dermatology.

Recommended for you

Archaeologists discover Incan tomb in Peru

February 16, 2019

Peruvian archaeologists discovered an Incan tomb in the north of the country where an elite member of the pre-Columbian empire was buried, one of the investigators announced Friday.

Where is the universe hiding its missing mass?

February 15, 2019

Astronomers have spent decades looking for something that sounds like it would be hard to miss: about a third of the "normal" matter in the Universe. New results from NASA's Chandra X-ray Observatory may have helped them ...

What rising seas mean for local economies

February 15, 2019

Impacts from climate change are not always easy to see. But for many local businesses in coastal communities across the United States, the evidence is right outside their doors—or in their parking lots.

The friendly extortioner takes it all

February 15, 2019

Cooperating with other people makes many things easier. However, competition is also a characteristic aspect of our society. In their struggle for contracts and positions, people have to be more successful than their competitors ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.