Vol. XVII · Eggs and Dairy Plate 2 of 10boiled eggs, soft-boiled, hard-boiled, jammy yolk, timing, egg size, fridge-cold, green ring, iron sulphide, peeling, 溏心蛋HT

Boiled Eggs.

Six minutes from the fridge into boiling water gives a runny yolk; seven, jammy; nine, just set; twelve, hard. A minute is a different egg.

Lowered into boiling water, an egg heats from the shell inward. The white sets first — its ovotransferrin firms from about 62 °C (VI.3) — while the yolk, at the centre and setting from about 68 °C, lags behind. The cook's choice is when to stop: a runny yolk (蛋黄流心), a jammy one (溏心蛋), just set, or fully hard. The time depends on the egg's size and how cold it started, as the square law and the starting gap predict (II.2).

Stop the cooking with an ice bath (XVI.2), or the heat stored in the white keeps cooking the yolk. Boil too long and the yolk's surface turns grey-green: iron from the yolk meets hydrogen sulphide released from the overheated white, making iron sulphide — harmless but unappealing, and avoided by not overcooking and by cooling fast. For peeling, start eggs in boiling rather than cold water (the white sets before it bonds to the membrane) and use eggs a week or two old (XVII.1). The workshop boils an egg.

Below: how set the yolk is at its centre and how set the white is on average for an egg of the size you choose, from the fridge or room temperature, against minutes in boiling water followed by an ice bath (thermal bench, course protein rates).

What you will learn

Time boiled eggs by size and starting temperature.
Explain why the white sets before the yolk.
Avoid the green ring.
Make eggs that peel cleanly.

Workshop

Thermal bench: egg as a sphere of the diameter chosen (large eggs about 45 mm), from 5 °C or 20 °C, lowered into boiling water, then 3 minutes in iced water. Setting from the course rates for ovotransferrin (white) and yolk proteins; yolk centre "runny" below 0.1, "jammy" up to about 0.6, set above 0.9.

Minutes, size and starting cold

For a large egg from the fridge in this model, six minutes leaves the yolk centre essentially liquid (0.00 set) and nine sets it (0.90). Starting at room temperature gains about a minute: seven minutes from room temperature sets the yolk centre to 0.23, against 0.01 from the fridge. A smaller egg needs a little less, a jumbo a little more.

Method: bring water to a rolling boil; lower the eggs in gently with a spoon (a pin-prick in the broad end can stop cracks); turn the heat down to a brisk simmer; time precisely; lift the eggs into iced water for at least three minutes; peel under running water from the broad end. For 溏心蛋 or ramen eggs, marinate the peeled jammy eggs in soy, mirin and water overnight. For a hard-boiled egg without a green ring, about 10–12 minutes and a fast chill.

At the stove

Boil four eggs from the fridge and take one out every two minutes from six to twelve, straight into iced water. Cut them in a row: the progression from runny to hard is the plate's curve.

茶叶蛋 (tea eggs) are boiled, their shells cracked all over, then simmered for hours in soy, tea and spices: the marbled pattern on the white is where the dark liquid got in.

Terms

Soft-boiled: Boiled until the white is set and the yolk runny.
溏心蛋: A jammy-yolked egg, often marinated.
Green ring: Iron sulphide on an overcooked yolk.
Ice bath: Iced water to stop cooking and help peeling.

Time boiled eggs by size and starting temperature; the white sets before the yolk. Chill at once to stop cooking and avoid the green ring; start in boiling water for easy peeling.

Sources

Egg proteins: ovotransferrin sets near 62 °C, ovalbumin near 80 °C, the yolk thickens near 65 °C and sets near 70 °C (H. McGee, On Food and Cooking, 2004, ch. 2; P. Barham, The Science of Cooking, 2001).
H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.