Egg
White sets at 62°C, yolk at 68°C. Those two numbers explain almost everything about cooking eggs.
Choosing
No cracks, and no sloshing when you shake it. In water, a fresh egg sinks; an old one floats, because its air cell has grown.
Fresher is not always better. For eggs that peel cleanly, a few days old is better, and slightly older whites whip higher. The reverse holds for dishes that need the white to hold together, like Gyeranjjim or a poached egg — those want fresh.
Temperature is everything
- 62°C — the white starts to set.
- 68°C — the yolk starts to set.
- Above 80°C — the proteins contract hard and squeeze water out: dry curds in liquid.
Which is why an Omelette and Gyeranmari are only tender over low heat, and why yolk-thickened creams like Chocolate Mousse are made over a water bath. Boiling times and the full reasoning are in Eggs.
White and yolk do different jobs
- Yolk — fat and lecithin, so it works as an emulsifier. That is the mechanism behind Carbonara.
- White — protein and water, so it makes foam. A trace of fat stops it whipping, so the bowl has to be grease-free.
Storing
- Three to five weeks refrigerated, ideally in the carton they came in — shells absorb odours.
- Pointed end down keeps the air cell at the top and they last longer.
- Leftover whites: 3–4 days refrigerated, 3 months frozen. Yolks: covered with water, two days.
- Boiled eggs keep a week in the shell, two or three days peeled.
Substitutes
In baking, one egg can be replaced by 1 tbsp ground flaxseed plus 3 tbsp water, left ten minutes. It does not replace the emulsifying or foaming function, so anywhere the egg is providing structure the result will differ.