Steaming
Steaming is a moist-heat cooking method where food sits above simmering or boiling water, in a covered pot, and cooks in the hot vapour rather than in the water itself. It is gentle, quick and fat-free, and it keeps more flavour and water-soluble vitamins in the food than boiling does.
Why steam cooks so well
At sea level, steam in an open pot sits at about 100 °C / 212 °F, the same as boiling water. The temperature isn't the trick. The trick is condensation.
Turning water into vapour takes a lot of energy: about 2,260 joules per gram, more than five times what it takes to heat that gram from freezing to boiling. When steam touches cooler food, it condenses back into water and dumps all of that stored energy straight into the surface. That is why a steamer cooks far faster than a 100 °C / 212 °F oven, where dry air carries heat poorly.
Because food never sits in liquid, less flavour, colour and nutrients leach out. Vitamin C and folate are water-soluble, and studies of broccoli and other greens generally find steaming keeps more of them than boiling. The moist air also stops surfaces from drying, so fish stays silky and dumpling wrappers turn soft and glossy instead of crisp.
The temperature ceiling
Steaming has a built-in limit. It can't go above the boiling point, so it never triggers the Maillard reaction or browns anything. That is a feature for delicate food and a drawback if you want crust. At high altitude water boils lower (about 95 °C / 203 °F at 1,500 m), so expect steaming to take a little longer.
Typical steaming times
Times start once the water is at a full boil and the lid is on.
| Food | Size | Time |
|---|---|---|
| Spinach, bok choy | leaves | 2–4 min |
| Broccoli, cauliflower | 4 cm (1½ in) florets | 4–6 min |
| Green beans, asparagus | whole | 4–6 min |
| Carrots | 6 mm (¼ in) slices | 5–7 min |
| Potatoes | 2.5 cm (1 in) cubes | 10–15 min |
| Fish fillet | 2.5 cm (1 in) thick | 8–10 min |
| Dumplings | fresh / frozen | 6–8 / 10–12 min |
Common mistakes
- Lifting the lid repeatedly. Each peek dumps the steam and the pot needs time to rebuild it.
- Packing the basket. Steam has to circulate. Leave gaps and keep to a single layer.
- Letting the pot boil dry. Use 3–5 cm (1–2 in) of water and keep a kettle hot to top it up during long steams.
- Overcooking greens. Past about 7 minutes, acids released from the cells turn chlorophyll olive-drab. Pull vegetables while they're still bright, or blanch and shock them for even more vivid colour.
No steamer? No problem
Set a heatproof plate on three balls of foil or a small inverted bowl in a wide pot, add water to just below the plate and cover tightly. A colander set over a saucepan with a lid on top also works. For a sealed, self-steaming parcel, see en papillote.
Chef Fizz says: Line bamboo steamers with cabbage leaves or perforated parchment and your dumplings will never stick. Bonus: the cabbage is a free side dish!
Questions
Is steaming faster than boiling?
For small pieces it is about the same, because both cook at roughly 100 °C / 212 °F. Steaming often wins overall because you only heat a few centimetres of water, so it comes to temperature much sooner than a full pot.
Why are steam burns worse than boiling-water burns?
When steam condenses on skin it releases its latent heat, about 2,260 joules per gram, on top of the heat of the hot water itself. Always tilt the lid away from you so the cloud escapes on the far side.
How long do you steam fish?
Roughly 8–10 minutes per 2.5 cm (1 inch) of thickness over a full boil. Fish is done when it turns opaque and flakes; Health Canada recommends 70 °C / 158 °F at the thickest point (USDA: 63 °C / 145 °F).
Should the water touch the steamer basket?
No. Keep the water level 2–3 cm (about 1 inch) below the food. If it touches, the bottom layer boils and turns waterlogged while the top steams.
Do you salt steamed vegetables before or after?
After. Salt in the water doesn't travel with the vapour, so season steamed food as soon as it comes out, while the surface is still damp enough for salt to stick.