Originally Posted by chopper
The jars seal. It's "canned".
Yes they do, and yes it is, but if there are any botulism bugs in the jar when it is sealed and canned, they will continue to grow unless the jar is kept in the freezer, in which case, all that hard work spent in sealing the jars is something of a waste time. I hope that the many experienced canners on this forum will forgive me for stating such basic information, but here's how it works.
Clostridium botulinum thrives on both animal and plant tissue (it loves asparagus!) and is anaerobic, so it can live in an oxygen free environment. One thing that will kill it is an acid environment. I believe that C. botulinum cannot live at a pH below 4.6, and when we make high acid jams and such (yum) the pH is probably closer to 4.0.
Unfortunately, some other nasties are not deterred by the low pH and so we subject them to the temperature of boiling water in a water bath for ten minutes. A weak spot on the lid pops down as the contents of the jar cool and contract, and the bottle is "sealed" or "canned. Unfortunately, this temp (212F) alone is not enough to kill the botulism bugs, so if the contents of the canning jar are not highly acidic, they will thrive. What will kill them is the high pressure, high temperature produced in a pressure cooker. Sparrowgrass already gave us a link with the government's figures for this.
But of course, if there are no botulism organisms in the jar when it is sealed, you won't get the disease. Perhaps because so few people can anything but jam these days, the national incidence of botulism is very low, less than 30 persons per anum, I believe. A third of those, however, are from Alaska, where, my late wife told me, the Inuit would thaw frozen meat and then freeze what was left for next time. I saw one case in London over fifty years ago. The patient was a Goanese seaman, and everyone thought that he must have an exotic tropical disease. Unfortunately, by the time that they discovered their mistake, he had died in great distress, so I am very careful about the handling and preparation of canned foods!