Saturday, September 27, 2008

Home Canning Warning

There are many benefits to home canning...
  • it saves money
  • it is healthier (you have control over how the produce is grown and processed),
  • it supports the local economy if you are buying produce from local farmers,
  • it does not need to be transported across miles to get from the farm to your table, thus reducing consumption of fuel,
  • it is better on the environment by reducing waste because jars are recycled from year-to-year, and
  • it gives a sense of accomplishment of a final product (after all the hard work put into growing the produce if you have a garden) that benefits your family...the jars always look so pretty lined up on the shelf!
However, it is important to understand how to do it correctly and safely. I am just beginning to learn...I know I have a lot more to learn and practice, but, because I work in public health, I am aware of the serious risk of botulism when home canning is not done correctly. (By the way, there is a risk of botulism if you are flavoring oils with garlic and herbs and it is not stored correctly, or improperly storing vacuum sealed bags as well.)

In fact there was a whole family poisoned by botulism toxin recently from produce that was not canned properly...this was not in Ashland County, by the way, but word spreads and CDC must be notified to fly in the antitoxin, so it is a big deal from the public health point of view (you don't know how many people could be involved initially and it is important to investigate the source and be sure no one else is at risk - this is also why it is against food establishment codes to sell home-canned vegetables at restaurants).

Botulism is rare (only about 145 cases are reported in the US each year) and foodborne botulism only accounts for about 15% of those cases. Clostridium botulinum is the name of a group of bacteria commonly found in soil. These rod-shaped organisms grow best in low oxygen conditions. The bacteria form spores which allow them to survive in a dormant state until exposed to conditions that can support their growth. When produce, especially low-acidic foods such as green beans, corn, asparagus, potatoes, and beets are preserved in jars, conditions could become right for the spores to grow and multiply. The spores become activated in a low acid, anaerobic (low oxygen) environment with temperatures ranging from 40°F to 120°F, having high moisture content, and lacking competing bacterial flora. This is why it is so important to carefully follow the safe procedure for processing all canned foods. (So, please don't try any "new" recipes that sound like a "short cut.") These are some suggestions from the experts on food safety of how to prevent foodborne botulism:
  • If consuming home canned foods, heat low acid foods to 176°F or boiling for 10 minutes and corn, spinach and meats for 20 minutes before consumption to reduce the risk of illness
  • Oils infused with garlic or herbs should be properly refrigerated (45°F) to prevent the growth of C. botulinum spores.
  • Canned food products, both home and commercial, should be inspected before use. Cans with bulging or damaged lids, leakage, or off odors should not be used because growth of the bacteria can often produce a gas, causing the can to expand. Throw out any damaged or expired cans.
  • Home canned foods should be canned in pressure cookers to ensure the proper time, temperature and pressure requirements to avoid the growth of the bacteria and spores.
  • If canning meats, use nitrites or salt in the brine in addition to heat to reduce the growth of C. botulinum.
  • Vacuum packaged meats should be refrigerated or properly stored in the freezer for extended use.
  • Keep hot foods above 140°F and cold foods below 40°F to prevent the formation of spores (be wary of cooking baked potatoes in aluminum foil and then not consuming them immediately).

Note: Home canning has been done by many people over many years. It is safe when done correctly (I am not trying to discourage anyone from learning or doing home canning - see those benefits I listed above), but it is also important to understand how and why it must be done correctly, especially for anyone who may be trying to learn how to do home canning on their own. (If I was not in public health, I probably would not have realized how serious of a risk botulism is because we don't ever hear about it.)

There is more information on Botulism including a USDA Home Canning Guide here and here

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