It’s Canning Season!

Canning is getting more and more popular among a younger generation that may not have had the influences of mother and grandmother to teach them about the finer details of the practice. Canning is a wonderful way to preserve fruits and vegetables, and a vital component of the “back to earth” movement. However, canning can be dangerous as well. Botulism is a major concern of improperly canned items.

What is Botulism?

Botulism is an illness caused by a bacteria, clostridium botulinum. The bacteria is found in soil, and can survive, grow, and produce a toxin in certain environments, like improperly canned foods. The toxin is a neurotoxin that causes paralysis and can lead to death, if not treated. Botulinum toxin cannot be seen, smelled, or tasted.

Botulism is an emergency. If you suspect you have food borne botulism, or someone you know, go to the emergency room or urgent care clinic right away.

Botulism Symptoms may include:

Double vision
Blurred vision
Drooping eyelids
Slurred speech
Difficulty swallowing
A thick-feeling tongue
Dry mouth
Muscle weakness   

Low Acid Foods = Greater Risk

Low acid foods in the canning world are foods that, when canned, have a higher pH level than 4.6 (they are more alkaline – remember that the lower the pH number, the higher the acidity). The low acid level of these fruits and veggies is not acidic enough to prevent the growth of botulinum bacteria.

Here are Some Examples of Low Acid Foods:

Green beans
All meats
Fish and seafood
Some tomatoes*

*tomatoes require added acid; citric acid or lemon juice for safe canning

Canning Safety Tips

Many cases of food-borne botulism have been the result of home-canned, preserved, or fermented foods that were contaminated. They were not canned correctly. Here are some safety tips to help ensure that foods are canned or preserved properly.

1. Follow the USDA Complete Guide to Home Canning Techniques ( – a lot of recipes do actually follow the techniques outlined in this guide, and it is available via PDF online. If you are new to canning, it is worthwhile to look through the USDA guide and ensure that the recipe you are following is using the correct acid ratios, pressure limits and times, temperatures, and water bath times. There is also the National Center for Home Food Preservation ( , which is an excellent resource.

2. Use the right equipment for the kind of foods that you are canning
This is important when canning low-acid foods. Pressure canning is the only recommended method for canning low-acid foods. Pressure canners are also extremely easy to use, and make the canning process go a lot faster.  Use a pressure canner that can hold at least four one-quart jars upright. Be sure the gauge on the pressure canner is accurate – gauges may be checked at county cooperative extension offices. Make sure all lid gaskets are clean. Vent the pressure canner before pressurizing and cool using the recommended steps. Use the up-to-date process times and pressures, jar size and method of packing food in the jar – all can be located in USDA Guide.

3. When in doubt, throw it out!
This is perhaps the most important. If you think that the canning process has been compromised, don’t eat the food. Also, here are some other indicators that the food may be contaminated:

  • jar is leaking, bulging, or swollen
  • jar looks damaged, cracked, or abnormal
  • jar spurts liquid or foam when opened
  • food is discolored, moldy, or smells bad


Image Copyright: <a href=’’>citalliance / 123RF Stock Photo</a>

Node Smith, ND, is a naturopathic physician in Portland, OR and associate editor for NDNR. He has been instrumental in maintaining a firm connection to the philosophy and heritage of naturopathic medicine among the next generation of docs. He helped found the first multi-generational experiential retreat, which brings elders, alumni, and students together for a weekend camp-out where naturopathic medicine and medical philosophy are experienced in nature. Four years ago he helped found the non-profit, Association for Naturopathic ReVitalization (ANR), for which he serves as the board chairman. ANR has a mission to inspire health practitioners to embody the naturopathic principles through experiential education. Node also has a firm belief that the next era of naturopathic medicine will see a resurgence of in-patient facilities which use fasting, earthing, hydrotherapy and homeopathy to bring people back from chronic diseases of modern living; he is involved in numerous conversations and projects to bring about this vision.

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