[John Chapman (OP)]

Thanks fishytails

So now that you've established that my microwave oven is rancid with rotten old food, what about the second part of my question:

Why does adding other vegetables to the mix (and I have recently found that it's the peppers that do it) deodorise the smelly veg?

[Chemistry4me]

It neutralises the sulphur compounds?

[John Chapman (OP)]

Aha! That sounds interesting. How's that work, then?

[Chemistry4me]

Well, do you believe this?

A piece of charcoal in the pot will neutralize the odor given out by the cabbage, boiled in the ordinary way.

http://chestofbooks.com/food/recipes/Clayton-Quaker-Cook-Book/Vegetables.html

[John Chapman (OP)]

Charcoal in the pot with the vegetables? Wow. I'd like to try that.

I once had the mechanism of the deodorizing power of charcoal pegged as a question for this forum. But I'd forgotten all about it. So...

How's that work, then? And can the mechanism transfer to peppers?

Any ideas, Chem?

[Chemistry4me]

Charcoal absorbs things like a sponge.

[Chemistry4me]

One teaspoon of charcoal has a surface area of more than 10,000 square feet.

www.oehc.ca/activated-charcoal.rtf

[John Chapman (OP)]

That is quite interesting although the evidence isn't supported very scientifically and it doesn't explain the mechanism. I wonder if that's true about one teaspoon having a surface area of more than 10,000 square feet.

Still, it doesn't explain how peppers absorb the smell. I suspect they may in some way be neutralising or counteracting the smell rather than absorbing it. Chemistry rather than physics.

[DrN]

I'm still confused as to why the veg would smell differently when steamed in the microwave than when steamed over a pan. I assume they taste the same? I generally only microwave-steam potatoes, broccoli and green beans, and I've never tried it with frozen veg, or even pre-packed pre-prepared veg, so perhaps I'm missing out?

[John Chapman (OP)]

I've just wiki'd activated charcoal and, in a nutshell, it says that charcoal absorbant properties work using Van der Waals forces throughout it's incredibly large surface area. It says that "one gram of activated carbon has a surface area of approximately 500 m²". I can't be arsed calculating a direct comparison with the "one teaspoonful & 10,000 square feet" that Chem4Me found but, if anything, the wiki reference sounds even bigger.

[John Chapman (OP)]

Hi fishytails

Sorry if that's not clear. The smell is exactly the same regardless of how it is cooked. Now I understand why you suggested it might be caused by old food in an unclean microwave.