What Causes Rubbery Egg Yolks?

When the eggs are subject to low-temperature environment, the egg yolk reduces its water content upon exposure to coldness. ... This phenomenon is called frozen gelation of eggs. The lower the storage temperature, the more likely the egg yolk will have a “rubber texture” after cooking.

What causes an egg to become tough and rubbery?

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.

Is an egg bad if the yolk is hard?

If the yolk of a hard-cooked egg has a green ring around it, this means the egg has been overcooked or was cooked in water with a high iron content. This egg is still safe to eat. If there is a blood or meat spot on the egg, it is still safe to eat and does not mean the egg is contaminated or has gone bad.