Raspberry/microwave sparks!

I thought I had posted this before, but apparently not. Not sure if this will gain as much press as the 'mentos in the diet cola' ones...

Back in late 2004 we were buying and using frozen raspberries for various culinary delights, and we found that when we tried to defrost them in the microwave that it caused sparks, arcing and burnt raspberries! It didn't happen with the other frozen products like blackberries or blueberries, just with the raspberries.

I sent an email to the company and asked if they were aware of it, and did we win the strange facts about XXX company's products award? No such luck, unfortunately.

A director of the company did email back to me and said that they tested the frozen raspberries in several different microwave machines and they all sparked. The manufacturers of the microwaves said that it could be the size and shape of the ice crystals. They were able to coax sparks from some frozen blackberries, but the raspberries always sparked.

I liked the opening sentence from the frozen raspberry supplier, 'Your email has certainly 'sparked' a reaction here...' Ha ha!

So, what is unique about the ice crystals in frozen raspberries that causes them to arc and spark in a microwave? Could this be a question for Dr Karl?

P.S. Kids, don't try this at home - your parents will not be impressed with a scorched non-functioning microwave machine, and the smell of burnt raspberries in the kitchen!