The standard way to hard-boil eggs-ten minutes in boiling water is far from ideal, according to physical chemist Herve This. Egg whites and yolks are made up of protein and water. yolks contain fat as well. As eggs cook, their ball protein uncoils into strands, and the strands bind together to form an intricate mesh that traps water, in essence, the proteins form a gel, a liquid dispersed in a solid. Boiling causes too many egg proteins to bind and farm dense meshes, yielding rubbery egg whites and sandy, grayish yolks.

But exploiting egg-protein chemistry allows egg cooking to be very precisely calibrated. Ovo transferrin, the first of the egg-white proteins to uncoil, begins to set at around 61℃. Ovalbumin, the most abundant egg-white protein, coagulates at 84℃. Yolk proteins mostly fall in between, with most starting to solidify when they approach 70℃. Using a laboratory oven, Dr. This cooks eggs at 65℃ for about an hour, timing not being critical. The results, with the whites delicately set and the yolks still orange and soft, make it clear why 65-degree eggs are becoming the rage among chefs in France. (Salmonella cannot survive more than a few minutes at 60'C, so a 65-degree egg cooked for an hour should be quite safe.)