Tag Archives: Clostridium botulinum

Get Ready Now for the Summer Harvest


If you are thinking about joining the trend in our communities to preserve food this summer, start planning and preparing now! Start by checking your equipment and supplies. Proper equipment in good condition is required for safe, high quality home canned food, for example.

If you’ve not yet purchased your needed equipment, there are two types of canners to consider: boiling water canners and pressure canners. A boiling water canner is used for canning acid or acidified foods like most fruits, most pickles, jams and jellies. Boiling water canners cost about $30-$100, or can be assembled yourself with a large stock pot, secure lid, and rack to keep jars off the bottom of the pot.

A pressure canner is essential for canning low acid foods such as vegetables, meats, fish, and poultry. Temperatures inside pressure canners reach higher than boiling water canners (for example, 240°F and above as compared to about 212°F). This is necessary to follow the tested processes available to be sure and kill the toxin–producing spores of the bacteria Clostridium botulinum.  If not killed, these spores can grow out and produce a deadly toxin (poison) in room-temperature stored jars of the low-acid foods mentioned.

You have two choices for type pressure canner: a dial gauge canner or a weighted gauge canner. Most steps in managing the pressure canning process are the same, but the two styles have different types of gauges to indicate the pressure inside the canner. Expect to spend $100-$150 or more on a pressure canner.

If you use a dial gauge canner, then it’s important to have the gauge tested for accuracy before each canner season or if you drop or damage your gauge. It isn’t as easy as it used to be to get gauges tested. Try a local hardware store or your local Cooperative Extension agent, even though not all still provide this service. For either type of canner, check that the rubber gasket is flexible and soft, and if it is brittle, sticky, or cracked then replace it with a new gasket. Also check that any openings, like vent ports, are completely clean and open.

You’ll also need jars, lids, and ring bands for canning. When getting started, new jars are a worthwhile investment (versus purchasing used jars from a yard sale or flea market) because very old jars may break under pressure and heat. Mason-type jars of standard sizes (e.g., half-pint, pint, and quart) for the tested processes available from science-based sources such as USDA and your land-grant university are recommended. Make sure those jars are manufactured and sold for canning purposes; not all glass and Mason-style jars are tempered to prevent breakage with the extreme heat and temperature swings during canning. When you actually get to canning your harvest, be sure to follow manufacturers’ advice for preparing your jars and lids. In addition to standard cooking utensils like cutting boards and bowls, a jar funnel, jar lifter, lid wand, headspace tool, and bubble-freer are items that you will want to have handy for canning.

If you are freezing your harvest, be sure to use packaging such as plastic bags or rigid containers that are intended for freezer storage of foods.  Not all plastics are the same, and you want materials that will hold up to freezer temperatures as well as protect your goodies from damaging air and mixtures of odors.

Growing your own? You may be lucky enough to have previously started keeping garden records so you remember the name of that great tomato or pepper variety you have liked this past year. If not, think about planning to keep records this year. A garden journal might include variety, seed source, date planted, date harvested, notes on how it grew and resisted disease, and your personal evaluation of the crop.

A final must is reliable, up-to-date canning and other food preservation instructsetp5ions. Specific kitchen equipment or ingredients could be needed to follow directions as they are written for food preservation. And in the case of canning especially, very significant food safety risks by following unsound recommendations. Reliable, up-to-date canning instructions are available at the NCHFP website, the USDA Complete Guide to Home Canning, So Easy to Preserve, or the county or local area Extension office in your state.


This entry contains information from Keep A Garden Record Book—Thomas Jefferson Did by Wayne McLaurin.

Botulism: Think Outside the Jar

Since it’s that time of year that foods may be prepared well ahead of time, then packaged and transported to be shared with family, friends, and co-workers, it seems timely to spread awareness about less-known situations that have the potential to lead to botulism: Did you know that it is possible for botulism to come from non-canned food items? As mentioned in a previous posting called “Botulism: Surprises”, botulism has been linked to other foods, including unrefrigerated salsa, baked potatoes in aluminum foil, garlic in oil, fermented fish, and honey. Following are a few true tales to provide important details and inspire caution…

In 1994, in Texas, 30 people were affected by an outbreak of botulism from restaurant dips made with baked potatoes wrapped in foil and left at room temperature (apparently for several days) prior to being used the dips. In this case, the spores of Clostridium botulinum (which are readily found in soil) survived the heating process (which is to be expected), remained moist, and were then so tightly wrapped in aluminum foil that oxygen was kept out of the packaging, creating an anaerobic environment in which the botulism toxin could form. Oil covering a food, as with garlic in oil, also creates an anaerobic environment.

real potatoes

Not even processing your homemade salsas but putting them in tightly sealed jars (again, an anaerobic environment) left at room temperature is a big risk. Botulism could result if the salsa is too low in acid, and other problems besides botulism could occur even in more acid salsas. Tomatoes (and figs and Asian pears) are borderline pH foods, so we see recommendations to add some acid to jars even before treating them as boiling water canned foods. Fermented fish and fermented vegetables that do not finish fermenting to a truly acidic pH are other examples of foods that might not be acidic enough to prevent the botulism-causing toxin from forming.

Another situation that has caused botulism is pickled eggs left at room temperature. In 1997, in Illinois, a 68-year-old man developed symptoms of botulism – double vision, inability to speak, difficulty breathing – that was traced back to homemade pickled eggs. Testing confirmed the presence of type B botulism toxin. To prevent the toxin from forming, pickled eggs should be stored in the refrigerator and only be at room temperature for serving time; limit their time in the temperature danger zone (40 degrees F to 140 degrees F) to no more than 2 hours. Pickled egg recipes and storage guidelines can be found on the NCHFP website.

Early in 2011, two people got botulism from eating commercially made potato soup intended for refrigerator storage but kept in their homes at room temperature.  One case was in Georgia and one in Ohio.  Both people bought the soups from a refrigerator case, left them out of the refrigerator at home for a long time and then tasted them.  Bad decision!  Each individual spent a long time in the hospital and then were transferred to rehab facilities with respiratory issues. Unfortunately we do not know the ultimate outcome today.

It may now seem like botulism can come from anywhere, but that’s not true; Clostridium botulinum bacteria require specific conditions to be able to grow and produce the botulism-causing toxin. Understanding what’s involved in the formation of the toxin will help you know how to prevent it:

In order to grow and produce the botulism-causing toxin, C. botulinum bacteria must be kept in a very low-oxygen (anaerobic) environment with a pH above 4.6 (low acid foods) and a relatively high moisture content.  If these conditions are met, any temperatures in a wide range around anyone’s “room temperature” and definitely above 40 degrees F will allow the bacteria to multiply and produce toxin.  (Sometimes the temperature even can be a little cooler than that for some types of C. botulinum and they will still multiply.)

Pressure Canner

Awareness and action is the key to prevention. To avoid botulism, avoid the risk of containing C. botulinum in a low acid, moist, anaerobic environment and if you do so (you canners out there know who you are), then be sure to process your low-acid food products in a canner equivalent to at least 240 degrees F (achieved when your pressure canner reaches the recommend amount of pressure, after venting, for your altitude) for the recommended amount of time.

Click here to view the full article of ‘Foodborne Botulism From Eating Home-Pickled Eggs —Illinois, 1997‘ from the Centers for Disease Control and Prevention. Here is the full publication ‘A Large Outbreak of Botulism: The Hazardous Baked Potato‘.  And here is the short story of botulism from potato soups in 2011.  

Ummm…what exactly is botulism? (Part III)

Botulism: Surprises

Before moving on to the brighter sides of home food preservation, a few more interesting and perhaps less known facts about botulism:

  • Home canned products may be the most well-known source of botulism, but in recent decades botulism has also been linked to unrefrigerated homemade salsa, baked potatoes in aluminum foil, garlic in oil, traditionally prepared salted/fermented fish, and honey (the primary cause of botulism in infants).
  • This might startle you, but we actually consume C. botulinum spores regularly and they generally do not harm adults. Adult human bodies prevent the growth of spores, such that no toxin can be produced.
  • However, spores have been found to germinate, colonize and produce deadly poison in the intestinal tracts of infants. Therefore, USDA recommends that honey is not given to children under 1 year of age and that fruits and vegetables be washed very well before fed to infants.
  • Clostridium botulinum toxin is among the most toxic substances known.
  • Cases of botulism have been reported in which people showed symptoms only 4 hours after ingestion. The longest time reported between ingestion and illness is 8 days.

Information in the entry comes from the USDA factsheet Clostridium botulinum and So Easy to Preserve.

Umm…what exactly is botulism? (Part II)

Botulism: Prevention

After reading last week’s entry you know where botulism comes from and the effects it has on people. But perhaps even more importantly, are you confident that you know how to prevent it?

There are essentially two ways to prevent botulism: 1) thermal destruction (heating) of spores and 2) inhibiting spores from germinating into toxin-producing vegetative cells.

Even in favorable conditions, C. botulinum vegetative cells and toxin should be destroyed when held at the temperature of boiling water (212°F at sea level) for a relatively short period of time. There are some other inactivation heat processes available for different types of food, also.  However, C. botulinum spores are much more heat resistant and need temperatures much higher than boiling to be killed in  reasonable times.  For home canning, we use temperatures of 240°F or above. It is very important to note that, unlike most bacteria, C. botulinum and other spores are NOT destroyed by normal cooking or boiling procedures. The spores require higher temperatures (240°F or above) that properly operated pressure canners create.

dial=gauge pressure canner

To prevent botulism, use approved processing methods and times as recommended by USDA. Carefully follow recommendations for pressure canning low acid foods. If you are still concerned if you did everything right, you can boil home-canned products in a saucepan on the stove for ten minutes before serving (add one minute more for each 1,000 of elevation).

Also remember that C. botulinum spores cannot germinate and then produce the toxin in pH levels of 4.6 or below. Acid foods and properly acidified food products have pH levels equal to or less than 4.6, so the toxin formation is prevented. Examples of acidified foods include pickles to which vinegar is added and salsa to which lemon juice is added.

pickled green beanspeach apple salsa

You can further help prevent botulism and other foodborne illness by practicing general food safety; refrigerate all leftovers within 2 hours after cooking, and after just one hour if temperature is above 90°F. Discard, without tasting, any containers of food that are swollen, bulging, leaking, or cracked. Also immediately discard any product that spurts liquid or foam from a container once opened (unless it’s carbonated and shaken, of course).

Information in the entry comes from the USDA factsheet Clostridium botulinum and So Easy to Preserve.