Toni, water boils at 212Âº F / 100Âº C; to kill the Clostridium botulinum, bacteria that makes botulism, and also de-activate any spores and botulism (a toxic product of the bacteria) you need to heat food to 240Âº. This can only be done under pressure. It can also be killed in an acid environment. If you don't kill them they can grow and produce a pretty poisonous sauce! I always thought tomatoes were acid but not enough. I've seen recipes lowering the acidity by adding lemon juice or citric acid but leaving well enough alone for fresh tasting tomatoes, you need to pressure cook. this bacteria is normally found in soil! read more here: http://edis.ifas.ufl.edu/fs104 http://www.bt.cdc.gov/agent/botulism/cl ... ontrol.asp http://en.wikipedia.org/wiki/Botulism http://www.hc-sc.gc.ca/fn-an/securit/ki ... nt-eng.php After researching botulism, I suddenly found myself more grateful than fearful of my new pressure canner. Mine says it can also be used as a pressure cooker but I can't imagine cooking in a 23 quart pot or cooking in aluminum... but I may need to feed a hoard fast someday, you never know!