Tomatoes on sale here during the winter don't taste as good as those available in summer. Does their nutritional value change too?

Mark Alberstat, Halifax, Nova Scotia, Canada

When retrieving some tinned tomatoes, my mum found the can bulging, evidently due to some gas produced, some of which bubbled to the top as it was opened. The inside of the tin wasn't coated as it should be and the metal had corroded.

I decided a little detective work was in order and after a bit of searching discovered this was due to hydrogen swell, a result of electrolytic action. A satisfactory explanation for most, but being an A level chemistry student with some knowledge of electrolysis I'd love to know exactly what compounds and ions are involved.

I noticed it first when I had a sandwich that had some tomato relish in it. As soon as I brought the sandwich to my mouth to take a bite, I immediately got a strong smell of acetone - at least that is the closest smell I can think of. It didnt smell like any kind of food and I couldnt smell it for long without having to take it away again it was so strong. I decided then that there was just something wrong with the sandwich. But later when I was chopping tomatoes I got the smell again, so I decided to test with a few other items - ketchup was the only other thing I had that gave me the same smell. I tested them and no one else smelt anything out of the ordinary. So presumably it was caused by some mucus in my nose at the time. Was it a chemical reaction in my nose that caused the strange smell?

2 days later and tomatoes smell normal again - the strange thing is, I still have a cold.