Vol. XVIII · Meat and Poultry Plate 6 of 11velveting, 上浆, 滑炒, 过油, starch coating, egg white, stir-fry, chicken, beef, 嫩, wok, Chinese technique, 腌TM

Velveting.

Restaurant stir-fried chicken is smooth and tender; home stir-fried chicken is often dry and stringy. The difference is a spoonful of starch and egg white.

Chinese cooks call it 上浆, "putting on a slurry": slices of chicken, pork, beef or shrimp are tossed with a little salt and Shaoxing wine, then with egg white and starch (cornflour or potato starch), sometimes a little oil, and left for 15–30 minutes. Then they are cooked briefly — passed through warm oil (过油, about 120–140 °C) or simmering water (滑水) for under a minute until just white — drained, and added to the wok at the end to finish with the sauce.

It works in three ways. The salt seasons and lets the thin slices hold water (XVIII.4); with only a millimetre or two to go, minutes are enough. The coating holds a film of water at the surface, which keeps the meat's outside near 100 °C while it lasts, instead of letting it sear and overcook (III.5); then the starch gelatinises (VII.1) and the egg white sets into a smooth skin that slows juice loss and catches sauce. And the gentle first cooking stops early, so the final stir-fry only heats the slices through. The workshop stir-fries 5 mm slices.

Below: juice lost by 5 mm chicken slices stir-fried in a hot wok for the minutes you choose, with and without a velveting coating (thermal bench: the coating as extra water at the surface), and the slice's centre temperature.

What you will learn
Workshop
Thermal bench: 5 mm chicken-breast slices from 5 °C stir-fried in a wok (contact cooking, turned every 15 s), then a minute off the heat. Uncoated: the usual surface water (0.12 kg/m²); velveted: a coating modelled as 0.6 kg/m² of surface water. Juice loss from each layer's highest temperature plus evaporation. A teaching model of the coating, not a measurement.

Starch, egg white, gentle first heat

In this model, after a minute and a quarter in a hot wok, plain slices have lost about 46 % of their weight, their centre at 93 °C; velveted slices have lost about 35 %, their centre at 85 °C, kept cooler by the water the coating holds. Leave them in for three minutes and the difference narrows (70 % against 61 %): the coating buys time, but a thin slice overcooks fast in any case. Thin slices cook in about a minute; the skill is to take them out then.

Method for 滑炒 chicken: slice 300 g breast thinly across the grain (XVIII.10); mix with ½ tsp salt and 1 tsp Shaoxing wine, then 1 egg white and 1 tbsp cornflour, then 1 tbsp oil; rest 20 minutes. Slide into oil at about 130 °C (or barely simmering water with a little oil), stir apart, lift out as soon as they whiten, about 40 seconds. Stir-fry the vegetables and sauce, return the chicken for the last 30 seconds. For beef, a pinch of baking soda in the marinade raises the pH so the fibres hold more water (VI.5) — a common restaurant step used sparingly, since too much tastes soapy.

At the stove

Stir-fry two batches of thin chicken slices for the same time: one plain, one velveted with egg white and cornflour. Taste both: silky and juicy against dry and fibrous.

Velveting is centuries old in Chinese cookery; 上浆 and its thicker cousin 挂糊 (batter coating, for deep-frying) are among the basic 刀工火候 skills taught in Chinese culinary schools.

Terms

上浆 (velveting)
Coating thin meat with salt, egg white and starch before cooking.
过油
Passing coated meat briefly through warm oil.
滑水
Passing coated meat briefly through simmering water.
挂糊
A thicker batter coating for frying.
上浆 — salt, egg white and starch — keeps a film of water at the surface so thin meat does not sear and dry; the coating sets into a silky skin. Cook briefly first, then finish in the sauce.

Sources

  1. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
  2. H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.