Blanching answers

Advice on blanching vegetables

April 21, 2009

I have a question regarding blanching. I read in some recipes to bring water to a boil and then drop in vegetables and cook for 1 to 2 minutes or whatever. At what point do I start counting? After the water returns to a boil, or when dropping in the vegetables? I have always wanted to know and never knew whom to ask. I hear you’re the guy to ask.
— Pam G., Brentwood, Tennessee

Blanching starts as soon as the vegetables hit the water, even if the boil stops briefly.

Your question reminds me, though, that recipes really fail us sometimes. Follow a recipe too closely, and your food’s deliciousness can be at stake. I know I complain about this a lot, but too often a recipe instruction like the one you mention doesn’t really get the point across.

As with most techniques, the exact timing of blanching is less important than the result. The correct amount of time for blanching, then, as with all cooking steps, is “long enough.” That might seem unhelpful, but it’s important to understand if you want to take responsibility for the quality of your food.

In culinary school, I volunteered to braise the fennel for our first-term final practical exam. I had cooked the recipe before, and it came out perfectly — tender with just a hint of firmness. But on exam day, I cooked it the same length of time, and it was comically underdone.

Maybe it was because hyper-antsy students were opening the ovens too often. But as I watched the chef struggle to chomp the fibrous bulb while scribbling unmentionables (hint: rhymes with “buster cluck”) on my team’s grade sheet, the lesson was clear: Recipe times are mere guidelines, not gospel.

Effective recipes tell you which result to look for, combined with a suggested time. For example: “To blanch the greens, cook them in a large pot of boiling, well-salted water until just tender, about 5 minutes.”

If the recipe won’t help you out, you have to plug in the logic yourself, depending on the goal. The two most common reasons recipes call for blanching are parboiling and color fixing.

Parboiling is cooking vegetables part way ahead of time, for quick finishing later. (If you’re a word nerd like me, be advised that “parboiling” used to mean “to cook through completely,” but confusion of the prefix “par” with the word “part” in the 1400s apparently led to the modern usage. You can thank me later when you win big on “Jeopardy.”)

For example, greens are often best when sautéed in garlicky oil. But some greens may require so long to cook that the garlic would burn and turn bitter. The solution is to blanch the greens until tender (a short time for spinach, longer for hardier greens) before finishing them with a brief sizzle in the sauté pan.

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Color fixing just refers to the fact that green vegetables are always brightest after blanching. As we all learned in science class, the cells of green plants like broccoli contain chlorophyll, which absorbs red and blue light for photosynthesis. But microscopic air pockets among the plant cells cloud the green color. When broccoli is blanched, the green gases expand and escape from the cells, and the green color immediately brightens.

Of course, as anyone who’s cooked much broccoli knows, the brightening effect of heat has limits. As the cells break down during extended cooking, the chemical alterations to the chlorophyll turn the florets a dull olive color, usually accompanied by a mushy texture and sulfurous stench.

For something like a crudités platter, blanch the broccoli just long enough to set the bright color. Do this by dunking the whole head in the boiling water, holding carefully to the stem. (The whole-head technique is much easier than bobbing for individual florets in a rolling boil.)

Additionally, blanching deactivates enzymes that can turn plants soft, brown, or otherwise unsavory. Take basil, for example, which turns an ugly dark brown (and eventually blackens) when cut. Blanching basil leaves for a few seconds before puréeing them with oil makes for a bright green garnish. Unblanched basil would result in a drab sauce.

Add lots of salt.
Use a big pot of boiling water.
Taste for doneness.
Drain into a colander.
Dunk into an ice-water bath.
Your veg are ready to go.

The secrets of successful blanching? More salt and more water than you probably think you need.

Salting the water liberally will season your vegetables evenly, and may also help maintain the chlorophyll’s brightness.

One of my chef-instructors at school used to say that blanching water should be 10 times saltier than the sea. Rather than get hung up on the difference between seven and 10 times saltier than the sea, I prefer TV chef Anne Burrell's guideline of “shockingly salty.”

A couple of tablespoons of kosher salt per quart should do the trick, but to be honest, I don’t really measure.

Boiling plenty of water is also essential for good blanching. Thomas Keller (sure, a total hack, but still) calls this “big-pot blanching” and explains that it minimizes the time required for the boil to resume. The goal is to blanch the vegetables as quickly as possible, because the less time they cook, the less their color will degrade.

As for timing, the best approach is common sense and testing during the blanch. As Keller says in The French Laundry Cookbook: “We don’t give times for big-pot blanching in the recipes. There is only one certain way to tell if a fava or a bean or a pea is done: Put it in your mouth and eat it.” Amen.

But guidelines are still helpful, especially to newer cooks. Tender leaves will only take an instant. Mark Bittman recommends beginning to check most other vegetables for doneness after 30 seconds.

The recipe may state a time, but start testing (tasting or piercing with a knife) before the deadline. In any case, the clock starts the moment the vegetables hit the water.

Once the vegetables are sufficiently blanched, it’s time to stop the cooking. The best way to do this is to shock in ice water; otherwise all your careful work will be undone as the vegetables overcook in their own steam.

Scoop out the vegetables with a strainer (or pour the hot water through a strainer), then dunk the strainer into a copious ice-water bath. The strainer keeps the ice cubes from getting mixed up with the vegetables.

If you forget and just dump the hot vegetables into the ice water in a panic, you’ll freeze your hands trying to fish them out. Or, um, that’s what I’ve heard, anyway. I mean, I would never make a mistake like that . . .

Based in Portland, Oregon, Hank Sawtelle has engineering, legal, and culinary degrees.

There are 7 comments on this item
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1. by Stephanie on Apr 22, 2009 at 7:15 AM PDT

I appreciate the information on blanching, but want to know the effect on the nutrition of the food. Most of the information out there today says not to cook vegetables in water because vitamins then leach into the water (and out of our food). I was all set to decide it’s okay to blanch and then use the water for stock, and then you mentioned how salty the water has to be....

2. by helenrennie on Apr 22, 2009 at 11:30 AM PDT

Hi Hank,

I love your column! What a great explanation. I give cooking classes and it’s always a hurdle to get people over the exact measurement and timing of the recipes. They often listen to them too closely when it comes to cooking and not closely enough when it comes to baking. It’s a shame you don’t live in the Boston area. I am looking for good culinary instructors.


3. by Rachael Warrington on Apr 22, 2009 at 12:50 PM PDT

I agree with Helen. I teach cooking classes, and share tons of recipes with parents. They all get to hung up on the exact wording and not on the nature of what they are cooking. One day steaks will cook in 10 minutes, the next it may take less time due to several things.
So thanks for the words of wisdom.

4. by Leta Merrill on Apr 23, 2009 at 8:25 AM PDT

Nice photos! I need to take a blog photo class from you!
I really appreciate your addressing of the recipe issue, I think for most of us it has been a lesson learned the hard way.:)

5. by Hank Sawtelle on Apr 28, 2009 at 11:34 AM PDT

@Stephanie - It’s true some micronutrients leech into the water. I don’t get too hung up on it -- I eat plenty of veg and I do not blanch everything I eat. If you want to reduce the salt and use the water for stock you can definitely do that. Your veg won’t be quite as green or well-seasoned, so it’s a trade-off.

6. by anonymous on May 24, 2012 at 4:55 AM PDT

I blanched broccoli and got a beautiful green. Unfortunately, I THINK I left it too long in the pan when I finally added it to the sauced meat I was cooking. How long can you add already blanched vegetables to meat when cooking?

7. by anonymous on Mar 5, 2014 at 10:58 PM PST

Thanks for the in depth column, but please don’t refer to Thomas Keller as a hack. It’s a very unsavory remark.

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Hank Sawtelle has engineering, legal, and culinary degrees, and an intense curiosity about food and cooking. Follow Hank’s blog, Sous Vide Jones.

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