Hugh,
RH’s question regarding whether frying will destroy the botulism toxin is an important one. Theoretically, all home-canned foods should be boiled upon opening for 10 minutes plus an additional minute for each 1,000 feet above sea level to be as safe as possible. This is from the USDA and CDC. Of course, boiling only raises the temperature to a maximum of 212 degrees Fahrenheit. Deep frying home-canned French fries at temperatures of 350-400 degrees does indeed destroy the botulism toxin completely. We usually fry our potatoes for 8-10 minutes. If you are roughing it and having to deep fry without your deep fryer, but you need to know when your oil is hot enough, here’s a tip: Drop a popcorn kernel into your oil. It will pop when the oil reaches 350 degrees. For more information on botulism check out the links to the USDA and CDC. However, by far the most helpful for our purposes is PickYourOwn.