On Food and Cooking

especially those bulging from the pressure of
gases produced by bacterial growth, should be
discarded.
The low pH (high acidity) of tomatoes and
many common fruits inhibits the growth of
botulism bacteria, so these foods require the
least severe canning treatment, usually about
30 minutes in a bath of boiling water to heat
the contents to 185–195ºF/85–90ºC. Most
vegetables, however, are only slightly acid,
with a pH of 5 or 6, and are much more
vulnerable to bacteria and molds. They’re
typically heated in a pressure cooker at
240ºF/116ºC for 30 to 90 minutes.