I love to can. I’m not sure why it’s called canning when you put the stuff in glass jars, but I do know that food safety is nothing to mess around with. I’ve been contemplating a post about why safe food handling and processing procedures are so important, wanting to pull out my old textbooks and share all of the nitty gritty details with you, and find share-able charts and stuff, but well, it just hasn’t happened. So instead, I’ll share a little bit of the stuff that’s just knocking around in my noggin, after many years of canning and a few years of food and nutrition courses in college (I was a nutrition major).
It’s not just about botulism!
Okay, so pretty much everyone knows that botulism is bad. Not everyone understands what it is or how it happens, and a lot of folks seem to think that it’s the only real concern with canning. It’s not, but before I get to that other stuff, let me give you a quick n dirty run down on the nasty little bacteria called Clostridium botulinum (aka C. botulinum)- and yes, the italics and underline are required, as that is the proper method for writing the scientific (Latin) name of an organsim. For the purposes of this post, I’m just going to call it Cb, though.
Cb, like many potentially dangerous or pathogenic bacteria, is all over the place and can easily contaminate your home processed foods. Cb, in and of itself, is not the problem- when a healthy adult consumes a few Cb microbes, they just pass through their system, and odds are good that the person will never even realize it. Not particularly pleasant to think about, but the reality is that it happens. The problems begin when Cb gets introduced into an environment it doesn’t like (referred to as a ‘hostile environment’ by the microbiology people), and then is put back into its happy place. Here’s why…
Cb likes non-acidic, anaerobic (ie, no oxygen) environments. It can survive temperatures well above boiling, because it has a special defense mechanism that most other nasties, like E. coli and salmonella, do not. When you stick Cb into an acidic or oxygen rich environment, it just grows a hard little shell, called a spore, and goes dormant. Consuming a couple of these spores is unlikely to cause a problem for a healthy adult because our bodies are not happy places for Cb. (For babies and immuno-compromised individuals, there could be very severe problems, but I’m not getting into that today, since this post is going to be long enough without even going there, LOL.) Okay, so it’s not a problem when it’s live and wriggling, and it’s not a problem when it’s dormant and in the spore, so when is it a problem then???
The problem occurs when Cb ‘hatches’ from its spore. You see, Cb itself is not toxic to us. That little spore shell, though? That is lethal! Botulinum toxin is actually a part of the spore shell. When Cb is dormant inside the shell and the shell is intact, the botulinum toxin is bound up in the shell and can’t get out. When Cb wakes up and cracks the spore, the spore shell begins to break down, and in the process, the botulinum toxin is released. (Think about how an eggshell contains calcium- the calcium can’t really be absorbed in any notable quantity until the shell is ground up.) It takes less than a single drop’s worth of botulinum toxin to kill a healthy person, and it is invisible. In high enough quantities, it will develop a truly nasty smell, but it will kill you long before you can smell it.
So let me take you through a canning scenario…
I have this lovely batch of beef broth made, with my jars, lids and bands all set to go into the canner- everything has been thoroughly cleaned and meticulously prepared according to the standard procedures set forth by the USDA. I pour the broth into the jars, keeping everything clean and tidy, and working with all the loving care I always put into every jar. I put on the lids and bands, tightening them to that magical ‘fingertip tight’ setting, using my handy-dandy torque wrench-type gizmo, load the jars into my canner, and process them according to my beloved Grammy’s recipe.
Bacteria are microscopic, and I didn’t see a couple of Cb’s get into those jars. Grammy’s recipe calls for a boiling water bath, and beef broth is a low acid item. This is going to be a big problem.
The Cb is in those jars, and the jars are in the hot water. When it gets hot enough, the Cb will undergo sporulation (where they develop the spore shell and go dormant). The water bath will remove most of the air from the jars, creating a very low oxygen environment. The jars will finish processing and be removed from the water bath, then set on the designated counter to cool for 24 hours, before being put away in a cool, dark place, as is generally recommended for storing home-canned goods.
So what do you think is going to happen when the jar cools off? Cb is going to ‘wake’ and shed its spore shell, and that shell is going to begin breaking down, releasing its poisonous contents, the botulinum toxin, into my beautiful beef broth! (sob!)
Now, here’s the nifty thing about science and technology. We know that Cb and the botulinum toxin (b-tox) in its spore shell can be easily destroyed- with the proper equipment. A boiling water bath is only going to get your jars up to somewhere around 212 degrees Fahrenheit. Cb and botulinum toxin (b-tox) can be destroyed at about 240F, which can’t be achieved in a hot water bath. It can, however, be achieved in a pressure canner.
I’m not going to get into the specific hows and whys of the pressure canner, but the thing you need to know is that it gets your jars hotter than a boiling water bath, and it is enough of a temperature difference to kill off the Cb and destroy the b-tox.
Let’s say we run that same scenario with a batch of water bath canned cucumber pickles. Are we going to have a problem? Probably not, since pickles are usually highly acidic. The Cb will go into its spore and even if we consume it (assuming we are healthy adults), it will just pass on through, leaving our bodies in the same state it went in.
So now that you know more than you probably ever wanted to about that nasty little sucker, let me move onto a quick overview of some other stuff that is good for a home canner to know.
Anyone who has ever forgotten about some leftover something-or-other in the back of the fridge knows that there is stuff other than Cb that can make food inedible. Mold. Furry, fuzzy, smelly, and weird colors. Yuck!! Mold also has spores, but they’re different from Cb’s spores. They’re softer and more fragile, and for those things, it’s the organism itself that is harmful to humans- not the spores. They can be killed by boiling temperatures. There are other non-mold nasties, like listeria and salmonella, but they, too, can be killed by boiling temperatures.
The trick is to get the contents of your jars up to the right temperature for long enough to kill all of those little buggers off! Just bringing the water bath canner up to a boil is not enough– it takes longer for the contents of the jar to get up to that happy temperature than it does for the water surrounding the jars (glass can act as an insulator). Plus, you need to keep it at that temperature for a certain amount of time to make sure the nasties are truly RIP-dead. Bringing the canner up to a boil may be enough to cause the jars to seal and lids to ‘ping’, but that does not mean that the contents are safe to eat! Any number of nasty little organisms may still be alive, inside that jar, ready to ruin all of your hard work!
The main factors that determine how long a product should be processed for is how thick it is (aka the viscosity) and its water content. For example, broth is very thin, so will not take long at all. Meat cubes, on the other hand, are pretty dense, so will take much longer. There are other factors that come into play, too, but that is the biggie. If there is too much variability in the viscosity of a product, from batch to batch, then the USDA will deem it to be an item that is not suitable for home canning (as happened with pumpkin butter). Some items, such as summer squash, tend to go pretty mushy when cooked, which means the consistency is too unpredictable to be deemed officially safe for home canning.
So there you have it. Some of the info that’s been knocking around in my noggin, waiting to be shared with you all. I hope that it makes sense and was easy to read. If you have any questions, or would like to share your thoughts on the topic, please leave a comment.
Happy (and safe) canning!