Heat & Cooking Methods

Steam / Zheng

Also: steaming, 蒸, zhēng, à la vapeur, mushi, kukus

Cooking food in the vaporous heat of boiling water without direct contact with the water itself, preserving moisture, nutrients, and delicate textures.

/zhēng (Mandarin, rising-level tone 1)/Chinese 'zhēng' (蒸) dates in culinary texts to at least the Zhou Dynasty (1046–256 BCE); steaming vessels (zèng, 甑) are among the earliest purpose-built Chinese cooking implements. The technique diffused throughout East and Southeast Asia through trade routes. Independent development of steaming also occurred in Europe and the Americas.

Definition

Steaming is a moist-heat cooking method in which food is exposed to steam — water in its gaseous phase at or above 100 °C (212 °F) at sea level — without being submerged in water. The food is placed above (never in) a liquid that is brought to a boil in a covered vessel; steam rises, condenses on and around the food, releasing its latent heat of vaporization (approximately 540 cal/g, far more energy per gram than boiling water) and cooking the food from all sides simultaneously. The result is gentle, even cooking that retains moisture, preserves water-soluble vitamins and pigments better than boiling, and leaves the surface of the food un-browned (no Maillard reaction occurs below around 140 °C). Steaming is the dominant technique across much of East and Southeast Asia. In Chinese cooking, zhēng (蒸) is used for dumplings (jiaozi, har gow, siu mai), fish, whole crustaceans, rice, eggs (chawanmushi-style steamed egg custard), and dim sum items; the bamboo steamer stacked over a wok of simmering water is the iconic vessel. In Japanese cuisine, mushi encompasses gentle steaming at temperatures below 100 °C (lowering the lid or using a trivet to trap less-full steam) for chawanmushi egg custard, which would set rubbery at a full boil. Southeast Asian applications include steaming banana-leaf parcels, glutinous rice, and whole fish. Western classical cuisine uses à la vapeur for vegetables and fish fillets to preserve clarity of flavor. Pressure steaming (above 100 °C, typically 115–121 °C in a pressure cooker) accelerates cooking substantially and is used for resistant vegetables, dried legumes, and in commercial canning.

In use

“Whole sea bass, scored twice on each side and draped with ginger and scallion, is placed on a plate inside a large wok, the lid sealed, and steamed over a hard boil for exactly eight minutes; sizzling oil and soy are poured over the fish tableside to finish.”

Related terms

Bamboo SteamerDim Sum Chawanmushi MantiIdliParchmentEn PapillotePressure Cooking

References

1.On Food and Cooking — Harold McGee
2.The Food of China — E.N. Anderson
3.Land of Plenty — Fuchsia Dunlop
4.Japanese Farm Food — Nancy Singleton Hachisu
5.Modernist Cuisine — Nathan Myhrvold et al.

Confidence: high

Notes

Why steam cooks efficiently

Steam at 100 °C carries roughly 540 calories of latent heat per gram that is released as it condenses on food — compared to water at 100 °C which can transfer heat only by direct contact and convection. This is why a small amount of simmering water produces vigorous, even cooking: the phase transition from gas to liquid is where most of the thermal energy transfers. The food never rises above 100 °C, however, which limits maximum temperature.

High-heat vs. gentle steam

Chinese cooking distinguishes between high-heat steaming (vigorous rolling boil, maximum vapor production — correct for dumplings, siu mai, bao) and gentle steaming (water barely simmering, often with the lid slightly ajar to bleed off steam and keep the temperature around 80–85 °C). The gentle method is essential for silky steamed egg custard (zhēng dàn, Japanese chawanmushi): too much heat causes the egg proteins to over-tighten, producing a pockmarked, watery, rubbery surface instead of a smooth, quivering gel.

Aromatics in the steam

Because steam passes through and over food on its way up, aromatic ingredients placed beneath (in the water) or around (in the steamer itself) can season the food lightly. Ginger slices in the steaming water, spring onion stalks in the bamboo tray, or kaffir lime leaves lining a banana-leaf parcel all contribute aromatic compounds that volatilize and condense on the food's surface.