What Is Blanching? Guide to Blanching Vegetables

Blanching vegetables involves cooking them quickly in generously salted water to draw out their vibrant flavors and colors. The dull color you often see in raw green vegetables occurs because of the layer of gas that exists between the pigment and the skin. Blanching them releases that gas, allowing the pigment to reach the surface of the vegetable. If you overcook a vegetable, its acids and enzymes escape, and the pigment seeps into the water. This process dulls the color.

When blanching, your vegetables can go from bright to dull and overcooked very quickly, so the challenge is to cook the vegetables without losing color. These important steps will help you get this right: use a large quantity of water, and use a generous amount of salt (about a cup per gallon of water). If you are planning on serving the vegetables later, have an ice bath ready top the vegetables from cooking and preserve its vibrant color.

Blanching how you keep your green vegetables green and crunchy, if don't want to eat them completely raw. It’s also an invaluable cooking technique used by chefs like Thomas Keller when snappy textures and precise, stunning visuals are required. Learn Chef Keller’s method for blanching asparagus below.

Shocking vegetables with an ice bath post-blanching immediately halts the cooking process. Just like a hard or soft-boiled egg, vegetables will continue to cook even once you remove them from the heat. A good blanch is like a freeze-frame: right when the vegetable’s color is brightest, when it’s crunch is crunchiest, that’s when you shock by placing in a large bowl of ice cold water.

It’s possible to blanch vegetables with boiling water or using a steam basket. Steam blanching, which takes a few minutes longer than your average blanching time, typically maintains more of the nutritional value than water blanching, dropping vegetables straight into boiling water, where nutrients can get extracted and lost forever.

• Crudite platter: One of the best applications for a bushel of freshly blanched vegetables is laid out on a platter (or over ice, if you’re feeling fancy) with a few good dip options, like hummus, salsa verde, or bagna cauda.
• Niçoise salad: This French classic is a prime opportunity for blanched greatness: pair snappy green beans and boiled eggs with oil-cured tuna, olives, boiled potatoes, and fresh tomatoes for a protein-packed salad, all nestled together and topped with a mustardy vinaigrette.
• Stir-Fry: A great stir-fry is a kaleidoscope of color and textures: the fluffy scrambled egg, soft-yet-crispy rice, brilliant green ribbons of bok choy and broccoli, with slices of bright orange carrot and pale green celery for a super satisfying crunch. Blanch each vegetable separately before adding to the mix.

1. 1. Fill a large pot with water to within a few inches of the top. You want to use a generous amount so that the water retains its heat when you add the vegetables.
2. 2. Bundle and tie 6 to 7 asparagus (depending on the size); asparagus tips are fragile, and bundling helps protect them from damage during blanching.
3. 3. Add salt to the boiling water and take a minute to let it return to a boil. Make sure you add enough salt to the water—your water should taste as salty as seawater.
4. 4. Place asparagus bundles in boiling water. Add only the amount of asparagus bundles to maintain the rapid boil. The blanching process may require several batches.
5. 5. After 2½ minutes, use the tip of a paring knife to check for doneness. If necessary, continue cooking until tender.

Note: If you’ll be working with the asparagus further—grilling it, for example, or preparing a sauce for it—shock in the ice water bath to stop the cooking process and cool it enough for you to work with. If you’re serving the asparagus immediately, simply cut away the twine and arrange the asparagus spears on a platter. Garnish as desired.

Learn more about cooking techniques with Chef Thomas Keller here.