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How do microwave ovens cook food?

Understanding The Microwave

Barbara Kafka (Chef and Cookbook Author) gives expert video advice on: How do microwave ovens cook food?; How is cooking in a microwave different from other types of cooking?; What should I know about microwave power levels? and more...

How do microwave ovens cook food?

First off, when I speak about the microwave, I want to explain to people that it means what its name says. Teeny weenie little waves - today they'd probably call them nanowaves - but they are actually microwaves, which means they travel a very short distance. What they do, basically - it's not totally true, but basically - they agitate water molecules and that friction creates heat. And most foods have some water molecules in them - vegetables, chicken, fish, whatever - and that's how it cooks.

How is cooking in a microwave different from other types of cooking?

A microwave oven exaggerates like crazy. You have to know that. It cooks from the outside to the inside in the same way that a cake bakes, but much more so. So you need to position foods so that the thicker part or the bonier part or the more solid vegetables is near the outside of the dish, and the softer, and more easily cooked foods are inside the dish - an even arrangement.

What should I know about microwave power levels?

One of the things they do with the microwave oven; is to have power levels, i.e. you buy an oven with a certain wattage, meaning output from electricity in. That has changed over the years – 700 used to be a high wattage, 400 used to be a low wattage. Today some of them go up to 1200 and 1400. The oven manufactures came up with the idea of levels; first it was just high and low, then it was high medium and low, then there was a whole bevy of things about how to cook your vegetables. Now, I have to tell you, that I have tried these things – forget it! Sorry manufactures – you don't how much my carrot ways, you don't know how big it is, you don't know how young it is – you don't know how it's going to cook. Follow recipes, follow recipes of people you trust – basically, of course, I mean follow my recipes.

What is 'standing time'?

Standing time used to be ubiquitous as a microwave cooking instruction. It meant that after you turned off the oven, you left the food in the oven and let it stand. I think the analogy was supposed to be to a rib roast which stands and the juices collect. This does not happen with a microwave oven. In my view, what it meant was that the people didn't really know how to use it, no matter what they said, and consequently this gave it a chance to even out. Which happens if you cover it the way I do. It evens out you don't have to have standing time. The one time I do use standing time, I think the only time I use standing time, is with rice. Because rice continues to absorb liquid as it sits, even after it has cooked. It may be tender to the tooth, but it may still absorb some more liquid. But it's not essential. But cover it loosely with a dish towel, clean of course, and let it set on a counter for a few minutes.

There are no USDA temperatures for microwaving food safely. The only thing they can tell you is what the end result should be, i.e. what the temperature of the finished cooked food should be. And if you have a handy dandy kitchen thermometer which I highly recommend, not just for the microwave, but for your regular oven, then you can take the food's temperature and you can see what they recommend.

How does wattage affect microwave cooking?

Wattage affects microwave cooking by making it slower or faster and sometimes more or less even. Like any piece of equipment you need to get to know your oven and you need to know what it's wattage is so that when you read a recipe you can follow it intelligently. Now I'm going to give you a favor, I have a website it is called bkafka.com and there is an ask and tell section there and if you send me your questions, if you have an older book of mine and you need to know how to update something, sooner or later, I don't promise right away, I will retest it and get it to you. But you have to send me the wattage of your oven.

Do microwaves make food 'radioactive'?

They do not make food radioactive. They die very quickly. They are short little, barely alive things. They don't make your food radioactive. Neon lights, on the other hand... But that's another story.

Does altitude have an effect on microwave cooking?

Altitude has effect on all cooking because water and so forth come to a boil at a different amount of time on top of a mountain. I happen to live on top of a very high hill, they're called mountains in Vermont, but honestly they're so old and weary they're hills. Anyhow, it's 1,500 feet above town. The microwave, cooking in the microwave makes much less difference than cooking on top of the stove because you are dealing in this enclosed environment and the environment is a law unto itself, so you're pretty much safe. It's not going to change markedly when you cook in a microwave oven at a high altitude.