Herve This on the Perfect Hard-Boiled Egg

One of the six classic French bistro dishes that Hervé This discusses in Building a Meal: From Molecular Gastronomy to Culinary Constructivism is hard-boiled egg with mayonnaise. Employing science rather than relying on old dicta, This explains how to achieve the perfect hard-boiled egg. First let’s start with the properties of the dream egg:

1. Its shell must not crack during cooking.
2. It must easily peel off from the egg once cooked.
3. The white must not be rubbery.
4. The yolk must not be sandy.
5. the egg must not smell of “sulfur” and the yolk must not be greenish.
6. The yolk must be perfectly centered in relation to the albumen, so that when sliced the egg exhibits a pleasing symmetry

Here’s what This suggests:

1. To prevent the egg from cracking, take a pin and make a small hole in the large end of the egg. The egg encloses not only the white and the yolk but a pocket of air and the little hole allows the air to escape rather than exerting pressure on the shell. The old dictum that adding salt or vinegar to the boiling water does not work.

2. However, placing the hard-boiled egg in vinegar for a few hours allows you to remove the shell without causing damage to the egg. The acid in the vinegar acts as a corrosive, attacks the shell and makes it easier to remove.

3 and 4. To get the perfect egg white and yolk they both need to coagulate. Ideally, the egg should be placed in boiling water for ten minutes. The egg white begins to coagulate at 61°C (142°F) and the yolk at 62°C (144°F).

5. The right temperature (below 100°C) also prevents the smell of sulfur and a green yolk preventing the formation of dihydrogen sulfide which also reacts with the iron atoms of certain proteins to create the greenish ring found in bad eggs.

6. To have a perfectly centered yolk use a wooden spoon, roll the egg around so that no one part of it is always facing upward; when the white coagulates, the yolk will therefore be perfectly centered. As This explains that when you boil an egg, it usually lies on its side in the pan, which means that the yolk floats to the upper part of the shell.