The Chemistry of Egg Cooking: How Eggs Get Hard and Custards Thicken

The most commonplace procedures involving eggs are also some of the most astonishing kitchen magic. You begin with a slippery, runny liquid, do nothing more than add heat, and presto: the liquid rapidly stiffens into a solid that you can cut with a knife. No other ingredient is as readily and drastically transformed as is the egg. This is the key to its great versatility, both on its own and as a structure builder in complex mixtures.

To what does the egg owe its constructive powers? The answer is simple: to its proteins and their innate capacity to bond to each other.