I think most cooks would assume that they know how to cook an egg: put it in boiling water for 10-15 minutes. But French cook (and molecular gastronomist) HervÃ© This disagrees:
"Cooking eggs is really a question of temperature, not time," says This. To make the point, he switches on a small oven, sets the thermostat at 65Â°C, or 149Â°F, takes four eggs straight from the box, and unceremoniously places them inside. "I use an oven in the lab; it's easier. But if the oven in your kitchen is not accurate, cook eggs in plenty of water, using a good thermometer." About an hour later—timing isn't critical, and the eggs can stay in the oven for hours or even overnight—he retrieves the first egg and carefully shells it. "The 65-degree egg!" he announces. The egg is unlike any I've eaten. The white is as delicately set and smooth as custard, and the yolk is still orange and soft. It's not hard to see why l'oeuf Ã soixante-cinq degrÃ©s is becoming the rage with chefs in France. (Salmonella can't survive more than a few minutes at 60Â°C, or 140Â°F, so a 65-degree egg cooked for an hour should be quite safe.)
But why does it work this way? Well, let This hit you with a little molecular gastronomy:
...[W]hen an egg cooks, its proteins first unwind and then link to form a rigidifying mesh. But not all its proteins solidify at the same temperature. Ovotransferrin, the first of the egg-white proteins to uncoil, begins to set at around 61 degrees Celsius, or 142Â°F. Ovalbumin, the most abundant egg-white protein, coagulates at 184Â°F. Yolk proteins generally fall in between, with most starting to solidify when they approach 158Â°F. Thus, cooking an egg at 158Â°F or so should achieve both a firmed-up yolk and still-tender whites, since at that low temperature only some of the egg-white proteins will have coagulated.
This proceeds to demonstrate the differences between eggs cooked at 65Â°C, 67Â°C, and 70Â°C -- they're surprisingly distinct, and he can tell the difference just by sight.