Blanching 101

by Mark R. Vogel

Blanching is a cooking technique whereby food, usually vegetables or fruits, are briefly immersed in boiling, salted water, and then submerged in an ice water bath, (known as "shocking"), to halt the cooking process.

Blanching is utilized to:

Soften food Preserve it's color Facilitate the removal of skin Eliminate bitter flavors

Softening Food

Heat can be transmitted to food via direct contact, e.g., a grill, or indirectly through a medium. In the case of roasting and/or baking, this medium is air. With boiling, it is obviously water.

Water is a far more efficient medium for transmitting heat than air. This is because water is denser. A food submerged in water has greater contact with the water molecules than the air molecules in an oven.

Place one potato in boiling water, (212 degrees), and another in a 400 degree oven, and the boiled potato will be done in half the time or less. Thus, boiling is a quick and convenient method for tenderizing food.

Sometimes the food just needs to be blanched and it's done. For example, if you were making an asparagus salad, 60-90 seconds, (depending on the thickness of the asparagus), is sufficient to produce ample tenderness.

On the other hand, blanching can be a prelude to a secondary cooking method such as sautéing. Sticking with our asparagus example, if you wished to sauté thicker asparagus, or white asparagus, which tends to be quite fibrous, you are likely to burn the outside before the center has cooked completely.

A brief blanch and the asparagus will sauté quicker and more uniformly. String beans, broccoli, and root vegetables are other common vegetables that may be blanched before their introduction to the frying pan.

Preserving Color

Green vegetables are green because of chlorophyll, their primary pigment. Chlorophyll's archenemy is heat which causes it to break down and form other compounds that are less green.

Despite the heat involved, blanching still preserves the vegetable's color. Here's how. Green vegetables are actually greener than they appear. Trapped within their cellular network are gases that partially obscure their hue by refracting light.

Sort of like looking at a colored object through a veil of smoke. The first thing the boiling water does is to allow the dissemination of these gases into the air and surrounding water.