Vol. XVII · Eggs and Dairy Plate 4 of 10scrambled eggs, omelette, curd size, heat, stirring, weeping, syneresis, French omelette, 炒蛋, 番茄炒蛋HT

Scrambled Eggs and Omelettes.

Scrambled eggs taken off at 70 °C are creamy; cooked on to 90 °C they are rubbery and sit in a puddle of water. Twenty degrees make the difference.

Beaten eggs are a mixture of white and yolk proteins with a setting range from about 62 °C (the white's ovotransferrin) to about 80 °C (ovalbumin), with the yolk proteins between (VI.3). As the mixture heats, the proteins unfold and link, trapping water in a gel. Stirring breaks that gel into curds as it forms: constant stirring over low heat gives tiny, soft curds (French-style creamy scrambled eggs); occasional pushing over higher heat gives larger, fluffier ones; a still pan gives an omelette, a thin sheet set from below.

Past about 80 °C the protein network keeps tightening and squeezes out its water: the eggs turn rubbery and weep (syneresis). So the rule for tender eggs is to take them off the heat while they still look slightly underdone — carryover finishes them (II.9) — and for scrambled eggs to add butter, cream or a little milk, which dilute the proteins and raise the setting temperature slightly. Chinese 番茄炒蛋 and 滑蛋 use hot oil and quick, large curds, taken off soft. The workshop heats beaten egg.

Below: how set the egg proteins are and how much water a teaching model says the curds squeeze out, against the final temperature of the eggs (course rates for white and yolk proteins, held one minute; weeping a teaching curve).

What you will learn
Workshop
Set fraction: average of ovotransferrin, ovalbumin and yolk proteins after one minute at the temperature (course rates). Weeping: a teaching curve rising past about 78 °C as the network tightens. Curd size depends on stirring, not shown by temperature alone.

Off the heat while still soft

In this model, eggs held a minute at 70 °C are about 0.60 set — a soft, spoonable gel; at 90 °C they are 1.00 set and squeezing out water (86 on the teaching scale), the rubbery, weeping scramble of a buffet tray. The difference between creamy and rubbery is mostly the last few degrees and the last minute.

Method for creamy scrambled eggs: beat eggs with a pinch of salt; melt butter in a non-stick pan over low heat; add the eggs and stir constantly with a spatula, scraping the bottom; when they are thick but still glossy and slightly loose, take them off the heat and stir in a little cold butter or cream to stop the cooking. For a French omelette: very hot butter, eggs swirled and stirred until just set underneath and soft on top, rolled out in under a minute. For 番茄炒蛋: scramble the eggs in hot oil into large soft curds, set them aside, cook the tomatoes with a little sugar and salt, and return the eggs at the end.

At the stove

Scramble two eggs over very low heat, stirring constantly, and two over high heat, stirring only now and then. Compare the curds: small and creamy against large and fluffy.

Salting eggs before cooking does not toughen them, as is sometimes claimed; salted beaten eggs left for 15 minutes cook more tender and moister, because salt slightly changes how the proteins link.

Terms

Curd
A clump of set egg protein.
Syneresis
A gel tightening and squeezing out its liquid; weeping.
French omelette
A rolled omelette, set underneath and soft inside.
滑蛋
Chinese "slippery egg": soft, silky scrambled egg.
Egg proteins set between about 62 and 80 °C; stirring sets curd size. Take eggs off while still soft: past about 80 °C they turn rubbery and weep.

Sources

  1. 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).
  2. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.