Blanch

Blanching means cooking food for a short time in boiling water and then plunging it into ice water. The quick heat sets the bright color of green vegetables, softens them slightly, and loosens the skins of tomatoes, peaches and almonds. The ice bath stops the cooking straight away. Blanching is also the step before freezing most vegetables.

How to do it

1. Bring a large pot of salted water to a rolling boil. Use about 4 liters (1 gallon) per 500 g (1 lb) of vegetables so the water stays boiling.
2. Fill a large bowl with ice and cold water.
3. Add the food to the boiling water in small batches.
4. Cook for the time it needs: 15 to 30 seconds for ripe tomatoes, 30 to 60 seconds for peaches, 1 to 2 minutes for spinach and peas, 2 to 3 minutes for green beans and broccoli florets.
5. Lift the food out with a slotted spoon or spider and drop it straight into the ice water. This is called shocking.
6. Leave it until cold, about as long as it cooked, then drain and dry it well.

How to tell it is done

Green vegetables turn a vivid, bright green and are crisp-tender: a knife goes in with a little resistance. Tomato and peach skins split or wrinkle and slip off when you pinch them.

Why it works

Short heat drives out the air trapped in the surface of green vegetables, so their color looks brighter. It also stops the enzymes that make frozen vegetables lose color, flavor and texture over time, which is why you blanch before you freeze. The ice bath keeps the inside from going on cooking.

Common mistakes

• Too little water. Adding the food stops the boil and the vegetables stew.
• Overcooking. Green vegetables turn olive and soft.
• Skipping the ice bath. The food keeps cooking from its own heat.
• Leaving food in the ice water too long. It gets waterlogged.
• Not drying the food before freezing or dressing it.

In recipes

"Blanch the almonds" means boil them for about a minute so the skins slide off. "Blanch and refresh" is the British way to say blanch and shock. Some recipes use blanch for a short cook before a second step, which is closer to parboiling.