This won't work as well on the yolk, which, while also protein-rich, has lots of fats and other properties that make it more difficult for it to become hard. By exerting mechanical energy in the whisking process, you cause the protein bonds to break, and subsequently re-connect. Once these new, strong bonds are formed, the egg stays in that state. The proteins have formed a network of strong, permanent cross-links. When cooking eggs, use moderate heat .
High heat causes the protein in eggs to become tough and rubbery.
When you use high heat to boil an egg, it causes a chemical reaction between the yolk and the white that leaves a green film around the yolk. That film is iron sulfide , caused by iron in the yolk reacting with hydrogen sulfide in the white. Inc. All rights reserved. Please Click Here for a complete list of previously answered questions. If you would like to ask a question you can click here .