Dangerous Canning Practices

Events of the past two years have prompted a phenomenal rebirth of interest in canning.  And it's been accompanied by the sharing of what "Grandma did" and what "Amish do," and therefore, there's no need to follow the guidelines from the US government's Cooperative Extension.  

Look, I'm quite well aware of all the crap and horrors associated with our government, but the Cooperative Extension has conducted some extremely well-done research in the name of helping us preserve our food safely.  They haven't been overtaken by drag queens who wear stilettos to work.  Yet.  (At least I don't think they have.  Please don't shatter my illusions.  There's enough going on already this week.)

So let's take a look at some of the practices touted as safe "because Grandma did it."

1.  Using a water bath to can meats and vegetables.  Yes, this had been (and maybe still is) a common practice. Meats and vegetables, all low-acid foods, were canned in a boiling water bath for several hours.  The internal temperature of the food in the jars can't possibly get any higher than 212°F.  However, a temperature of 240°F must be reached in order to kill the bacteria that cause botulism.  So how come we don’t hear about a lot of Amish dying from botulism?  Well, some undoubtedly did die.  However, they also boiled their canned meats and vegetables for at least 10 minutes after opening them, which inactivates the botulism toxin.  If everything is done perfectly, and there is no taste-testing before the food has been boiled, and there are no splashes or spills to contaminate other food, then people may not get sick.  But it’s just not a chance worth taking. 

2.  Canning butter and cheese.  There are numerous websites and blogs providing instructions for both.  Some even acknowledge that the FDA hasn’t approved the practice, but then go on to say it’s just because they haven’t tested it. And that’s not quite true.  (But we don’t want to let something like the truth get in our way.)  Canning butter and cheese is not recommended because neither practice is safe.  Butter is 16% water.  It is a low-acid food.  What bacteria thrive in an anaerobic (oxygen-free), low-acid environment?  Our friends Clostridium botulinum.  Ah, but the home-canned butter proponents assert that the oven is at 250°F, so the bacteria are killed.  Unfortunately, that is not true.  While the oven may reach 250°F, the contents of the jars do not.  Then the home-canned butter people say that the C. botulinum bacteria are found in the soil, and the butter has never been anywhere near the soil.  Even if that is the case, what many people do not realize is that the bacteria can become airborne.  Most cases of infant botulism are not actually traced to honey.  Interestingly, many occur in infants who live near active construction sites—because the bacteria in the soil got into the air and inhaled or ingested. The bacteria could just as easily find their way into the butter in your kitchen.

3.  Canning bacon or other cured meats.  The canning of bacon, ham, and other cured meats is also not approved by the FDA or cooperative extension.  The concern is that the nitrites could somehow affect the bacteria.  However, uncured bacon and ham are basically pork.  And pork is safe to can.  If you decide this is a risk worth taking, keep in mind that bacon should not be rolled in parchment (as some advise to keep it in strips).  The jars must be packed as for any other food so that heat transfer can occur and the jar interiors reach the necessary temperature to kill the C. botulinum bacteria.

4.  Canning unapproved recipes.  The concern with unapproved recipes is that the acid balance may not be right.  If the acid balance is too low and the food is canned in a water bath, botulism may develop. 

5.  Canning dry beans without presoaking or cooking.  Here the fear is that the beans don’t have enough time to soften and that the interiors don’t reach 240°F.  In the interest of full disclosure, I did can beans this way a few times.  I always had an unusually high seal failure rate. I do not do this anymore.

6.  Re-using canning lids.  The ever-escalating price and difficulty in finding canning lids has prompted some home canners to turn to re-using lids.  It’s a practice that is definitely not recommended.  The seal failure rate is higher and there is always the risk of having a lid that will stay depressed even when the jar isn’t actually sealed.  However, when people can’t even find lids, they start taking chances.  As long as the lid securely seals—be sure to check before opening the jar—the food inside is safe.

7.  Oven canning.  Back in the early 1900s, to about 1943, oven canning was a thing.  Food was placed in the jars, the lids applied, and then processing occurred in the oven.  Unfortunately, every once in a while a jar exploded, sending glass shards everywhere, including into the face and arms of those doing the canning.  See, canning jars are made of annealed glass, not tempered glass.  They aren’t designed to withstand rapid changes in temperature that occur in ovens when the element turns on and then off. 

8.  Dry canning.  This is distinguished from oven canning in that it is used for dry goods like cereals, grains, pasta, rice, etc.  The food in placed in a heated jar in the oven with the lid off.  The food is then heated to about 200°F for 20-30 minutes. (Temperatures and times vary, but they’re in this range.)  There is the same risk of the jars shattering as with oven canning.  Beyond that, one of the principles of storing food for as long as possible is to keep it cool.  Heating the food in the oven drastically shortens its shelf life.    In addition, heating the food may cause some moisture to be released, which is then trapped in the jar when the lid is applied, increasing the risk of spoilage or bacteria growth. 

9.  Baking in canning jars.  This became a little bit of a fad about 10-15 years ago.  People began baking bread in the jars and then capping them when they came out of the oven to create a vacuum seal as the bread cooled.  So here we have two problems—the jars risk shattering in the oven while the bread is baking, and then when the jars are sealed, they create a low-acid environment perfect for botulism to develop.  The only baking that can safely be done in canning jars is when the jars are in a water bath, like for making cheesecake.  The water bath mitigates drastic temperature changes that could otherwise cause the glass to shatter. 

10.  Using glass jars not meant for canning.  With fewer foods being sold in glass jars, this is becoming less of an issue that it was for our grandparents.  Back in the 60’s and 70’s, mayonnaise was sold in glass jars that had the same size lid as canning jars.  Debate raged back and forth on the safety of re-using these jars.  Some said always, some said never, and some said just with water bath canning.  So what’s the truth here?  Some of those old mayo jars were, in fact, made of annealed glass that is used in canning.  Some of them even had a tiny Ball signature logo on the bottom of the jar.  So while most canning jars have a large logo of some sort on the side of the jar, not all do. Some have a tiny one on the bottom.  Even the Cooperative Extension offices from around the country disagree.  Some say to never reuse jars—even the Atlas ones (which aren’t actually canning jars) that Classico spaghetti sauce comes in.  Others say they are fine for water-bath canning.  No one recommends them for pressure canning.  Of those that say they are fine to re-use, all concur that the jars are thinning and that there is a higher risk of the jars breaking, particularly if they have been scratched. 

Practices #1 through 9 above are all related to food safety.  In addition, practices #7 through 9 also involve issues of operational safety.  With practice #10, there is no concern for food or operational safety.  The only issue, assuming the lid and band fit, is that the jars are thin and so they might break.  However, this only occurs in the water bath, not before or after.  It makes a heckuva mess and wastes food.