Now, those who know me well will agree with me when I say that there are two things that I really enjoy in life – chemistry and cooking! Recently I’ve been combining the two and learning more about the chemistry of food. I do intend to do some more posts on this area in future, as there’s just so many places I could go with this that it was hard to choose!
The white of an egg (known as the albumen) contains a large amount of protein, specifically a type called globular proteins, so-called because they have a roughly spherical (globe-like) shape. As we apply heat to the egg (like when frying an egg or making an omelette), the extra energy causes these proteins to move around more vigorously, colliding with each other and weakening the bonds between the different protein strands. As these bonds become weaker and weaker, their globe-like structure starts to unfold and the protein becomes “denatured”. These strands of proteins are then free to make these bonds with each other, causing it to coagulate (which is why the egg whites go from transparent to opaque as the egg is cooked). Overcooking creates too many of these bonds, so the proteins join together too tightly and you end up with rubbery eggs.