This is not an update; it is a random thought.

[brooksmoses]

Fact 1: Microwave ovens work because they produce microwaves tuned to a vibratory frequency of liquid water.

Fact 2: Microwave ovens are rather poor at defrosting chicken; the parts that get defrosted first become partly cooked by the time the remainder of the chicken is defrosted.

Question Arising From These Facts: Would it be possible to build a microwave oven that was tuned to a vibratory frequency of solid water that would defrost chicken properly?

Comments

[lisajulie.livejournal.com]

I didn't know that the vibratory frequency of solid water is different from that of liquid water. I thought it was a molecule by molecule thing.

Hmm.

[brooksmoses]

It mostly is, but I think the intermolecule bonds in ice would be strong enough to affect it. Or, more accurately, I know that they are, but I don't know if it's enough to create an effect that actually makes a noticable difference.

Hmm; I could look this up, rather than speculating. And it seems from this page that the frequencies in ice are about 7% or so higher.

More than that, however, it appears (reference here) that microwave ovens aren't exciting vibrational modes of the nuclei; they're exciting something else that I don't quite understand that involves rotation and electron clouds. Water in ice can't really rotate much, and so ice is practically transparent to the waves in microwave ovens -- the frequencies involved are on the kHz range for ice, rather than the GHz range for liquid water. Which indicates that making an ice-tuned microwave defroster may be rather difficult.

[oneironaut.livejournal.com]

I'm not sure it would help you that much, if it would be possible, which I don't know. Microwaves cook from the outside in just like every other kind of radiation I'm familiar with, so with a large enough piece of chicken you'd probably still wind up with the outside cooked, though possibly not as much.

You could try putting the chicken in a plastic bag and putting the plastic bag in a container of water, then heating the whole shebang on medium (in your current, existing microwave). It'd take much longer, but it might also cook the chicken less -- I'm guessing; it just came to me.

[brooksmoses]

Actually, microwaves, like all other forms of radiation, don't cook "from the outside in" -- they cook inward and outward from a distribution of photon absorbtion sites that extends into the volume of the material. For infrared, the penetration depth is negligible, and so it might as well be from the outside in -- but for microwaves, the average penetration depth is intended to be somewhat deeper than the thickness of what's being cooked, so a lot of the photons go through and get reflected back, and the rest land in a fairly even distribution throughout the interior of the stuff. And, if the microwaves are focused so they're more intense in the middle, you do get more cooking on the inside than the outside.

(Yeah, ok, so you said large enough, and it would be true for sufficiently large things, though "large enough" is probably a half-meter-diameter chunk from some giant mutant killer chicken.)

Anyhow, my chicken tends to get defrosted and cooked in bits on the middle of the sides, and stays frozen at the tips. What's going on is that when a bit of chicken gets defrosted, it suddenly has liquid water in it, and so that's a very opaque bit in the middle of this large mass of mostly-transparent chicken, and so all the photons stop there, and it gets hotter and cooked while the frozen parts aren't getting many photons to defrost them.

I will have to try the chicken-in-water idea, though; that does sound like it might work.

[mittelbar.livejournal.com]

I think you'd need something tuned to the vibratory frequency of a chicken.

[oldsma.livejournal.com]

I know that this is not what you want to hear, but I have just given up. I thaw chicken on a plate in the refrigerator and get perfectly satisfactory results.

I have cooked boneless chicken breasts from frozen in the 'wave. But those are relatively thin and homogeneous, and I almost always cook it sealed up with some flavorful liquid.

MAO

Short answer...

[seawasp]

... no.

Longer answer:
The microwaves are ABSORBED by the water molecules, which then vibrate faster. It has nothing to do with vibratory frequencies of the material (that sounds almost Golden-Age SFish). As the energy absorption is done on a molecular scale, it cannot tell the difference between liquid, gas, and solid phases.

Re: Short answer...

[brooksmoses]

Hmm -- I had forgotten that I needed to be a bit more clear on that. After hanging around spectroscopists for most of my grad school career, I tend to use "vibratory frequencies of the material" in this sort of context as shorthand for "vibratory frequencies of the molecules in the material".

And (see the link I posted in another comment) the molecular-scale absorbtion can indeed tell the difference between liquid and solid phases; when the molecules are in a solid, the intermolecular forces contribute to holding the atoms in relative position, and so the resonance frequencies are a bit higher. The interactions with microwaves are a bit more complicated than simple vibratory resonance, but it turns out (see the second link) that ice is practically transparent to the microwaves in microwave ovens even though liquid water absorbs them fairly well.

Interestingly, you can even tell the temperature of a gas by looking at its absorbtion spectrum. But that one's much simpler physics -- for an immobile molecule, you get sharp absorbtion peaks. As the temperature of the gas increases, the molecules move faster and faster, and so you get doppler effects that broaden the peaks, and by measuring the width of the peaks, you can tell the temperature.

Re: Short answer...

[seawasp]

Okay, you kicked my metaphorical ass around on that. At least you didn't begin it with "Ryk, you ignorant slut." ;)

If that is the case, then it should be possible to design one that shifts its frequency, if frequencies can be controlled accurately enough, to affect frozen water preferentially.

Of course, I just use my own microwave defrosting approach which avoids cooking the bird in places, but that approach requires that you experiment to know the characteristics of your particular oven.