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Why and How to Blanch and Shock Vegetables

By Cook's Illustrated Published May 2009

This classic pair of techniques turns raw vegetables perfectly crisp-tender for serving with dips on a crudite platter or in salads. It also seasons them and ensures that their color will be vibrant.

What is blanching?

Blanching involves briefly dunking fruits or vegetables in boiling water to set their color, flavor, and texture. It’s a classic method for tenderizing hard vegetables (such as carrots, green beans, or broccoli) to serve on a crudite platter or in a salad, or for eliminating bitterness in vegetables like broccoli rabe before a second cooking method (such as sauteing) is employed.  


What is shocking?

Shocking, a step that typically follows blanching, involves plunging just-blanched vegetables into ice water to immediately stop the cooking process. Doing so keeps the vegetables’ color bright and their texture crisp-tender.


How to blanch and shock vegetables


This method is for 1 pound vegetables that have been cut into evenly sized pieces. Cooking times will vary depending on the type of vegetable and the size of the pieces. 


  1. Bring 2 1/2 quarts water to boil in large saucepan over high heat. Add 1 teaspoon salt and vegetable, return to boil, and cook until pieces are bright green and crisp-tender.

  2. Meanwhile, fill large bowl with ice water. Drain vegetable in colander and transfer pieces immediately to ice water. When pieces no longer feel warm to touch, drain in colander again and dry thoroughly with paper towels. Transfer pieces to gallon-sized zipper-lock bag, seal, and refrigerate until ready to use, up to 3 days.  


Should the pot be covered or uncovered after adding the vegetables? 

Some sources claim that the lid must be kept off to prevent trapping acids from the vegetables in the cooking water, which could turn them brown. But after blanching batches of broccoli, green beans, and broccoli rabe in both covered and uncovered pots, we found that the lid made no difference. The pH (acid) level of the water was identical between batches, and the vegetables looked and tasted exactly the same.