When you learn about canning, you learn about botulism. Or at least you learn that botulism is a fatal illness lurking in every ‘improperly’ canned jar of food waiting to kill unsuspecting novice canners and cocky grandmas who do not precisely follow every step of modern instructions approved by the National Center for Home Food Preservation (NCHFP).
But not being people to follow directions ‘just because’, we had to do a little more research on botulism. I mean, how does it get into the jars in the first place? And really, an illness can’t live in a jar, a virus or spore or bacteria can, so exactly what are we dealing with here? And what about all those recipes for Pear Cardamom Butter and Strawberry Basil Jam I see in cookbooks that don’t have the NCHFP stamp of approval, what’s wrong with them? Well, have we got answers.
Botulism is an illness caused by the toxin produced by the bacteria Clostridium botulinum. The bacteria exists in soil and can be on any of the vegetables you pick and can. BUT the bacteria isn’t thrilled about life in the soil and stays holed up in its endospore waiting for better conditions. Before the bacteria will produce its harmful toxin it goes through (1) activation, by being heated up, (2) germination, when it discovers it’s in a lovely warmish, anaerobic environment and so breaks hibernation and begins to metabolise and (3) outgrowth, finally turning into a vegetative and reproductive bacteria cell. And until it starts reproducing, it doesn’t make toxin, and is therefore not harmful to humans. So fresh veggies are a-ok.
The canning process is great for Clostridium botulinum. The bacteria might be on any vegetables you are putting in to jars and then you boil them (activation) to seal the jars (anaerobic environment) so they can be stored at room temperature (warmish environment). Boom! They start reproducing and making toxin. The botulinum toxin is extremely powerful, so very small amounts (<100 nanograms) can still kill you. Meaning, it doesn’t really matter if the canned goods sit for 2 years or 2 days, botulism is still a risk.
So why aren’t people dying of botulism left and right? First, botulism shuts down your muscles over the span of hours, or even days. Your eyelids droop, your limbs go numb, you might faint, and then, your lungs can fail. Botulism can be fatal, but only if it advances so far that you stop breathing. In the meantime, most people are able to get treatment. In the US, there are about 30 cases of foodborne botulism a year (mostly in Alaska, because they have way more Clostridium botulinum in their soil) and only 4% of those are fatal. Second, it is possible to kill the bacteria or create inhospitable conditions for the bacteria when canning food (and most people do one of these two things).
Pressure canning brings canned food up to temperatures above 250°F which kills the bacteria. Or, you can water bath/boil can foods that have high acid, specifically pH below 4.6. Tomatoes (with added acid) and fruits are high acid, asparagus and green beans get pressure canned. Either way the bacteria never gets a chance to settle in and reproduce, so it never makes it’s poisonous toxin. And that is the root of all those canning rules. Note, you still boil high acid foods for so long in order to raise the temperature above 180°F to kill molds and yeasts. Because moldy food tastes bad, and because mold can raise the pH of the food, creating nice, cozy conditions for our friend Clostridium botulinum.
Now, a couple of questions that still need addressed:
Does that mean I’m allowed to water bath/boil can any foods I want as long as I know their pH is below 4.6 and not worry about botulism?
Yes. You would use a pH probe that can handle moisture and high temperatures and simply measure the pH of your food before canning. These run about $200 or we would totally have one.
What’s up with honey? I’ve heard it gives babies botulism.
Honey, like most things from outside, can contains Clostridium botulinum. The spores don’t like high sugar environments though, and so don’t reproduce in honey even though we store it for long periods at room temperature. But babies less than 1 year old have not fully developed intestinal microflora (all the fun things that live in our intestines) and their intestines are a perfect environment for Clostridium botulinum to grow and reproduce. If a baby is fed honey (or dirt, in some cases) the bacteria can start growing in their gut and cause infant botulism. Adults don’t have this problem because our intestines are less friendly to the bacteria.
I think my canned tomato sauce might have botulinum toxin in it, what should I do?
If your canned food smells funny, the metal lid is bulging, or you have some reason to suspect the presence of toxin, do not eat the food. To dispose of it properly you should boil the food for 30 minutes then dispose of it somewhere where children and animals can’t get at it. Boiling the food should denature the toxin, but consumption is still not advised. And remember, very little toxin is necessary to cause botulism, so don’t taste the food at all.
In conclusion, everything they tell you at the county extension home preservation workshops is correct. Just now we’ve learned why all those rules matter.