An important word about home canning of vegetables (see links for more information)
People still canning green beans at home using the boiling water canner instead of a tested pressure canning process are risking food loss and even worse, possible death or serious poisoning. We are receiving phone calls from people canning dozens and dozens of jars of green beans in boiling water and then losing all that work and food due to spoilage. Beans canned this way looked fine coming out of the canner, but are now turning cloudy and jars are popping open, even sometimes with force. These beans are definitely spoiling from being underprocessed. But it could be worse: even if the jars still look good, it is possible that they contain botulism toxin from this unsafe canning practice.
Jars of improperly canned vegetables and meats can contain the deadly botulism toxin without showing signs of spoilage such as being seen in the reports mentioned above. Those that do show signs of spoilage could also contain botulism toxin because they are showing other signs of underprocessing.
Spores of Clostridium botulinum bacteria, as found naturally in soils, are very, very heat resistant. Even hours in the boiling water canner will not kill them if they are inside your jars of beans. Left alive after canning, they will eventually germinate into actively growing bacterial cells that will produce a deadly human toxin when consumed. The bacteria like the conditions inside closed jars of low-acid foods (such as vegetables and meats) sitting at room temperature, so they must be killed during the canning process for safe storage.
You can find the USDA-recommended procedures for canning green beans at home here: http://www.uga.edu/nchfp/how/can_04/beans_snap_italian.html
The list of available vegetable canning processes is found at this menu:
and those for tomato and tomato products here:
We do not have home canning procedures to recommend for vegetable, meat, poultry or seafood products not found on this website.
You can read a little more about botulism and ensuring safe home canned foods here: http://www.uga.edu/nchfp/how/general/ensuring_safe_canned_foods.html
and principles about safe canning at home here: http://www.uga.edu/nchfp/how/general.html
Please be safe when canning foods for you and your family! Knowledge and recommendations change over time with scientific developments. You should use up-to-date recommendations and methods and not just rely on practices of past generations.