A Moment of Science

The Denatured Egg White

Were you ever curious how does an egg white turn into an opaque gel?

Eggs in a carton

Photo: Darrren Hester (flickr)

Applying heat to an egg white creates an opaque gel.

Have you ever wondered how heating an egg white turns that uncooked clear goo into an opaque gel?

How It Works

Well, that transparent goo is made of mostly water and proteins. Each protein is a long strand of amino acids that you can think of as a string of green and red Christmas lights. The green lights are hydrophilic amino acids, which attract water, and the red lights are hydrophobic amino acids, which hate water.

Each protein is coiled up in a big clump so that most of the water-loving green lights point outwards from the mass while most of the water-hating red lights point towards the inside to keep dry.

These coiled up proteins float around in small clumps allowing light to easily pass through the goo and provide little structure, so the goo is clear and liquidy.

Heating the goo causes the coiled up proteins to unwind, or “denature”, exposing the water-hating red lights to water.

To keep dry red lights from neighboring proteins glue together forming small nets of denatured proteins.

The Opaque Gel

Heat continuously applied to the goo produces a snowball effect as more proteins are denatured and aggregate together producing many additional small protein nets, which in turn glue together into bigger and bigger nets; giving structure to the goo and blocking light from passing through it.

Eventually via this process the egg white is transformed from a once clear and gooey substance into an opaque gel.

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