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Whenever I see a recipe which requires me to blanch vegetables for a few minutes, I microwave them instead. It's sometimes faster, I don't have to get a pot dirty, and I don't usually have to dry the vegetables afterwards. The microwave seems to do a very good job of par-cooking any vegetable which is cut up into small, uniform-sized pieces.

However, I've never seen a mainstream cookbook recommend microwaving instead of blanching. Is there a reason for this? Am I losing flavor or texture I would get with blanching? Or is this just one of those bits of propaganda one learns in Chef School, like how garlic presses are evil?

So, is microwaving vegetables to cook them a fine substitute for blanching them, or am I Doing Things Wrong?

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6 Answers 6

up vote 5 down vote accepted

My kitchen manager (fine dining restaurant) said that that the only thing a microwave should be used for in a professional kitchen is to heat water.

Microwaving tends to dry out the outside of vegetables, and hurts both texture and flavor. Proper blanching takes about 5 minutes once you have water at a boil, and maintains both the crisp, fresh flavor and full texture. Blanching also tends maintain color better, because the outside of the vegetables heats to the same extent as the inside, and this is doubly true if you use an ice bath to cool vegetables after blanching.

So yes, you are Doing Things Wrong. That said, we all take shortcuts at times, and microwave ovens do work rather well for thawing frozen vegetables. With frozen vegetables you've already lost a lot of the texture, so the microwaving doesn't do much further harm.

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Hmmm. I don't find that it dries out the outside of vegetables at all, except maybe that it doesn't add moisture the way a pot of water does. Also, since microwaves penetrate around an inch into the vegetables, for pieces less than 2" thick, the inside heats the same as the outside. I think this calls for a blind taste-test. –  FuzzyChef Dec 2 '11 at 4:49
BTW, I'm not saying this answer is wrong. I'm just saying that it has the tone of "recieved wisdom" rather than tested knowledge. I do agree with the comment about color though; blanching is better for bright colors, no question. –  FuzzyChef Dec 3 '11 at 6:07
Well, it's not just received wisdom. The microwave periodically does ungodly things to frozen spinach when I thaw it; I posted a question about it here a while back. I've also seen it dry out broccoli pretty badly as well. Also, the flavor and texture of stuff is never quite the same as thawing it by a steamer or in the toaster oven. –  BobMcGee Dec 4 '11 at 1:15
BMG: certainly there's differences. I take your point about leafy greens, which it tends to burn. Peas, carrots, green beans, diced potatoes, beets, etc. work perfectly well, though -- better than blanching if you are avoiding dilution of flavor. –  FuzzyChef Dec 4 '11 at 18:11
@FuzzyChef ...doing things wrong? Hardly...see these folks, for example: chefsteps.com/activities/…. ...not sure this answer should be marked as correct. I wouldn't call it "blanching", but you can use your microwave to cook veggies well. –  moscafj Jul 14 at 17:37

The main difference between microwaving and blanching is you can add salt to the water.

Proper blanching takes 1-5 mins depending on what your blanching and how soft you want it. There is no issues using a microwave you still have a container to clean. Microwave will save you about 5-10 mins waiting on the water to boil but considering you usually have to cook other things, what I do is first thing out on a pot of water prep/cook other things blanching something I do when I'm done with everything else considering I dont want the veg sitting there to long anyways considering its still cooking after you take it out of the water.

Personally I don't like microwaving veg cause I have never found one to cook the food evenly, compared to blanching.

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Microwaves do not heat food, they activate the water molecules in the vegetable and cause it to boil. This is why melting things like chocolate take a long time to heat and meat doesn't roast.

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I guess this is marginally an answer to the question - you're saying that it's bad because it boils water in the vegetables? It also sounds like this is a bit of a misunderstanding, though. Sure, it's true that microwaves work best on water, but it heats up that water, it doesn't immediately boil. If the food contains plenty of water (as vegetables do), that heat transfers quickly to the rest, so heating up the water is basically the same thing as heating the food. –  Jefromi Jul 14 at 17:30

Much depends on how you cook your vegetables in the microwave. I like to add butternut squash to pad out Chicken Maykupi (my own completely inconsistent curry recipe, using whatever comes to hand, and whichever spices I fancy on the day) and reduced the amount of chicken needed. If I add it raw, it's never cooked enough, if I add it cooked it falls apart. So I dice about half a squash into 3/4 inch cubes, put it in a bowl with a splash of water (2 tbsp-ish), cover with film and microwave for 4 minutes (850W). It works a treat every time, and takes less time than boiling a pan of water to achieve the same result.

My rules of thumb for microwave cooking of veg are: always cover with film (or loose-fitting lid) cook for half the time, give it a good shake, then finish off. Always cook for less time than you think, then give it another 30-60 seconds if necessary. Don't get obsessed with always using full power. 50% power for 50% longer can give a better result with heftier veg (e.g carrots). Use little water so that it gets absorbed rather than rinsing vitamins etc away.

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Wrong?? Not really for it's a shortcut and an easier way of doing things, however think about this the next time if you're planning to blanch or cook your vegetables in the microwave- do you know that the microwave works by radiating heat around the food and as you said it cooks from inside out, and once again radiation- thus this leads to an unhealthy life style.Besides that, if you manage to blanch the vegetables the right way you will enjoy them much more better as they still contain the vitamins and the minerals in them. Oh ya!! Another thing to remember is over cooking of vegetables is rather much more simpler to achieve by cooking in the microwave.

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Sorry I have to -1 this: microwaves do not work by radiating heat around the food, nor are they proven to lead to an unhealthy life style. The suggestion that blanching keeps the vitamins and minerals where microwaving doesn't is also suspect. This answer is more suited to a question on Skeptics.SE –  JoeFish Jul 30 '12 at 18:38
Just how does a microwave oven remove vitamins and the minerals? In the lab your basic test for this shows they are removed over time in hot water by the osmosis process, hmm that's sounds like blanching? You must have got the two confused :-) –  TFD Jul 30 '12 at 23:25
Since a microwave is just a high frequency radio wave, it cooks by a process called dielectric heating, which basically results in certain molecules vibrating and therefore generating heat. The radio wave is absorbed by the first thing it hits that it is "in tune" with it, e.g. water, oil. It therefore can only heat the outer layer of the food it is cooking. The inside can only be heated by thermal conduction. Try cooking a lump of frozen beans or minced meat to check this process out :-) –  TFD Jul 30 '12 at 23:32
Boiling a pot of water can be very hazardous, just check the government accidents register! Nothing is simpler than placing a container with a loose fitting lid of fresh or frozen vegetables into a microwave oven. They should be first washed and cut into even pieces. Cook for a few minutes, and then wait a minute or two before opening and serving :-) –  TFD Jul 30 '12 at 23:37

There is also another reason for not microwave your veggie as in here. (Look for hobodave's answer)

You never know that the veggie can catch fire in the microwave as some veggies have high concentrations of metals such as magnesium, iron, and zinc, which might catch fire inside the microwave.

Hope it help you.

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The discussion there seemed to establish that it takes more than just high mineral content for this to happen, and I think we'd know by now if things like broccoli had any chance of starting fires. –  Jefromi Dec 2 '11 at 17:00
This sounds like an urban myth to me. –  FuzzyChef Dec 3 '11 at 6:06
Generating Fireballs with a cut grape in a microwave oven: youtube.com/watch?v=vb6WCkC0K1I –  Wayfaring Stranger Jul 30 '12 at 19:51

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