Temper, temper

Eggs are a wonder of the world, capable of turning potential birds into real birds, supporting a soufflé, making nog and other custards, and bringing disparate ingredients together in a bit of harmony that would make the United Nations proud. There are nearly 3 sesquitillion techniques for working eggs properly into food, some of more general use than others. Today I'm going to tell you the secret of working eggs into hot liquid without scrambling it or otherwise turning it into a solid mass, a technique called tempering.

At the simplest level, an egg is a combination of fat, water, and protein. There's about 1000 times the amount of water than protein in an egg, but any given protein is around 1000 or so times as large as a water molecule. In the uncooked state, the proteins are curled up together, like a shiny new slinky. Cooking the egg causes the protein to unwind, just like the time your little brother got ahold of the slinky and decided to test it's marvelous stretching capabilities.

The reason the egg becomes solid is because the proteins start sticking to each other, making a nice three-dimensional structure. This is the equivalent of your brother having a sleepover, where twenty of his closest friends brought all their Slinkys, and they randomly grabbed the ends of the Slinkys and started running around the room like monkeys hopped up on red bull. The Slinkys would get tangled together in some points, stretched out in others, and pretty soon, nobody would be able to walk through the room because Slinkys get in their way. This is why the egg turns solid, and it's also why you can't see through it after it's cooked, because light can't pass through, either. All the water from the egg is stuck in-between the slinky chains, like your brother's friends.

Keep cooking it, though, and it takes the party too far. The proteins get too tight, and the metaphorical children in the slinky chain start realizing that metal kinda hurts when it gets to tight, so they slip out of the protein net and into the freedom of the living room (or frying pan, depending on whether you're following the metaphor or the actual event). This makes the egg tough and nasty.

For a basic egg, this happens at relatively low temperatures (145^A^0 to 180^A^0F, depending on which part of the egg). This means that if you throw egg into a boiling liquid, it's going to cook the egg on contact, which is likely not what you're going for, especially if you want to thicken a sauce. To spare your guests from a b~A(c)chamel ~A! la scrambled egg, the trick is to add a little of the hot liquid into egg mixture first. If your volume of cold egg is significantly greater that the warm or hot liquid, chances are that the egg will integrate some of the liquid before heating up too much. As the liquid will likely contain fat and/or water, this will decrease the protein-to-liquid ratio in the egg, meaning it will have to raise its temperature even more in order to form the slinky chains. It's like taking the sleepover to the nearest football field and putting in 2000 more children without adding more Slinkys - there's only so many ways that the slinkys can twist together in that much space.

Once you have enough of your liquid incorporated, you can safely add the tempered egg back to the hot liquid and reap all of the benefits that egg will provide you.