How to Blanch Vegetables (Times and Ice Bath Method)

To blanch vegetables, cook them briefly in a large pot of boiling salted water, usually 30 seconds to 3 minutes depending on the vegetable, then plunge them into ice water to stop the cooking. Blanching sets bright colour, keeps a crisp-tender texture, and stops enzymes from spoiling vegetables you plan to freeze.

Why blanching works

It brightens green vegetables

Raw green beans and broccoli look slightly dull because tiny pockets of air between their cells scatter light and hide the green pigment, chlorophyll. When the vegetables hit boiling water, that air expands and escapes, and the cells fill with water. Suddenly you can see the chlorophyll clearly, and the vegetable turns vivid green.

Keep cooking too long, though, and heat plus the vegetable's own acids convert chlorophyll into olive-brown pheophytin. That is why overcooked broccoli turns khaki. A short blanch followed by ice water gets the bright colour without the drab.

It stops enzymes

Vegetables keep living after harvest. Enzymes such as lipoxygenase and peroxidase keep breaking down flavour, colour, texture and vitamins, even in the freezer, just more slowly. Brief heating inactivates them. Unblanched frozen green beans develop hay-like off-flavours and toughen within weeks; blanched ones keep for 8 to 12 months.

It cleans and softens

Blanching also removes surface dirt and microbes, loosens skins on tomatoes and peaches, mellows harsh flavours in cabbage or onions, and wilts greens for easy freezing.

Why so much water?

Use at least 4 litres (1 gallon) of water per 500 g (1 lb) of vegetables. A large volume of boiling water holds a lot of heat, so cold vegetables do not drop the temperature much. If the water stops boiling for more than about a minute, the vegetables sit in hot-but-not-boiling water and cook unevenly, losing colour. Return to a boil within 1 minute is the target.

Steps

1. Bring a large pot of water to a rolling boil and salt it. Use about 4 L per 500 g vegetables. Salt seasons the vegetables from the outside in.
2. Set up a bowl of ice water next to the stove. Use roughly equal amounts of ice and water, at least 2 L in total.
3. Trim and cut the vegetables into even pieces. Same size means same cooking time.
4. Add the vegetables in small batches so the water keeps boiling. Cover the pot if needed to speed the return to a boil.
5. Boil for the recommended time, tasting as you go. Start timing when the water returns to a boil. Pull a piece and bite it: it should be bright and crisp-tender.
6. Transfer immediately to the ice bath. Use a spider or slotted spoon. Stir so they cool evenly. Leave them in about as long as they cooked.
7. Drain once fully cold and dry well. Spread on a towel. Water left on the surface dilutes dressings, splatters in a hot pan, and forms ice crystals in the freezer.

Blanching times

Times are for typical home pieces. The longer times are guidelines for freezing; for eating right away, aim at the shorter end and taste.

Common mistakes and fixes

• Dull, olive-green vegetables: cooked too long or the pot was covered with a tight lid for the whole cook, trapping acidic vapours. Shorten the time and chill immediately.
• Unevenly cooked: overcrowded pot or mixed sizes. Use more water, smaller batches, and even pieces.
• Watery, bland vegetables: not enough salt, or they sat in the ice bath too long. Salt the water and drain as soon as they are cold.
• Vegetables clump in the freezer: spread dry pieces on a tray to freeze individually, then bag them.
• Adding baking soda to keep things green: it does keep chlorophyll bright, but it makes vegetables mushy and destroys some vitamins. Skip it.

When to blanch

Blanch before freezing, before crudités, to par-cook vegetables you will later sauté or grill, and to prep vegetables for a dinner party so they only need reheating. For eating right away, steaming keeps more water-soluble vitamins.