You might occasionally come across a recipe that instructs you to blanch one of the ingredients before doing something else to it, like peeling it, stir-frying it or adding it to a salad.
Now, a well-written recipe will not only instruct you to blanch the thing, but will also briefly explain, and describe, what you are to do (and perhaps why you need to do it).
But not everything in the world is how it ought to be and that includes recipes. So let's talk about what blanching is, what the technique accomplishes, and when you might want to use it. That way, next time you come across the instruction to blanch something, you'll know exactly what it means.
What Is Blanching?
Blanching is a food preparation technique in which food is briefly immersed in hot liquid, like boiling water or oil, often but not always as a prelude to cooking it further. Fruits, vegetables, and nuts are the foods that are most frequently blanched, each for different reasons.
Sometimes it might be to soften it, or to loosen the skin to make peeling it easier, or simply to brighten the color of it.
Note the word "briefly" in the description above. Different recipes will call for different blanching times, but with blanching, times are measured in terms of seconds rather than minutes. Typical blanching times range from 30 to 60 seconds.
What Is Shocking?
Blanching is often done in conjunction with another step, known as shocking, which involves plunging the blanched item directly into an ice water bath, so as to stop the cooking that was initiated in the blanching phase.
This is a clue that blanching is more of a prep technique than a cooking technique. Blanching does not, and should not, cook the food. If the food is going to be cooked, that will happen later. Otherwise, blanched food is still considered raw.
The key with shocking is that you don't want to let the food sit in the ice water for too long, or it will start to absorb water and become soggy. What you want to do instead is just let it chill until the food is no longer warm, then drain it thoroughly and either store it or set it aside for whatever the next step is. You don't need to get it fully cold all the way through, but it shouldn't be warm to the touch.
When to Use Blanching
As we said, blanching softens vegetables and it also intensifies their colors. Whereas long boiling will turn green vegetables like asparagus or green beans a drab olive color, 30 seconds of blanching will turn them a bright vivid green. The same is true for the orange color of carrots.
Freezing can likewise cause the colors of veggies to turn drab, so blanching is a common step as a preliminary to freezing.
Vegetables such as green beans are often blanched in order to enhance their natural green color, as well as softening them. You'd want to blanch and shock green beans before adding them to a Niçoise salad, for example.
Another common use for blanching is to soften vegetables so that they can then be quickly cooked over high heat, like in a sauté or stir-fry. The reason being, high-heat cooking methods involve short cooking times, which isn't always enough to soften firm vegetables like carrots and broccoli.
On the other hand, cooking them longer will tend to overcook the other items in the pan. The solution: blanch the firmer vegetables separately, then add them to the pan with the other items.
A similar case is when we're adding raw veggies to a salad. Blanching and shocking is a good technique to use for vegetables that will be featured in salads. They're softened just enough so that you can eat them more or less raw, but they won't be excessively difficult to chew. And it also brightens the colors, making for a more visually appealing salad.
Other Uses for Blanching
Another use for blanching is to help loosen the skins on tomatoes, peaches, and other foods. If you're making your own marzipan, for instance, you'd need to blanch the almonds to remove their skins first.
Blanching also comes into play when preparing white stocks such as chicken or veal stock, with the bones being blanched beforehand in order to rid them of impurities.
Blanching is also an excellent technique for preventing avocados from turning brown.
Finally, when making French fries, the cut potatoes are often blanched in medium-heat oil, then cooled before frying them a second time at a higher temperature. This two-step procedure ensures that the fries are cooked all the way through (the first step) and also crispy on the outside (the second step).