On Food and Cooking

up into a compact wad whose shape is
maintained by bonds between neighboring
folds of the chain. In the chemical
environment of the egg white, most of the
protein molecules accumulate a negative
electrical charge and repel each other, while
in the yolk, some proteins repel each other
and some are bound up in fat-protein
packages. So the proteins in a raw egg mostly
remain compact and separate from one
another as they float in the water.
When we heat the egg, all its molecules move
faster and faster, collide with each other
harder and harder, and eventually begin to
break the bonds that hold the long protein
chains in their compact, folded shape. The
proteins unfold, tangle with each other, and
bond to each other into a kind of three-
dimensional network. There’s still much more
water than protein, but the water is now
divided up among countless little pockets in
the continuous protein network, so it can’t