"O.K. Some of you physicians or biologists out there correct my impression that botulism, even in canned foods thought to be properly canned and sterilized, is a risk often forwarned by swollen cans. If so, how do you tell if the swollen can is from heat alone, or Clostridium botulinum growth?"

I'm neither a physicist nor a biologist, but I doubt that the trunk of a car gets hot enough to perceptibly swell a can, at least where I live. (But in Death Valley or the Sahara--who knows?) So I'm going to treat any swollen can as suspect. The good news is that I have been eating canned food for a good many years, and I've never even seen one that was swollen, let alone opened one that was spoiled. Rotate, rotate, rotate.... <img src="/images/graemlins/cool.gif" alt="" />