Home Canning Risks - Spoilage and Botulism Basics

Quart jars of homemade tomato sauce cooling on a cutting board, with a cone strainer resting beside them.

9.6.25
by: Jill@321Oak
Pennsylvania, USA

Home Canning Risks: Spoilage Happens

While there is plenty of discussion on the internet and elsewhere about home canning safety, particularly when it comes to botulism, I don’t think anyone would argue seriously with this premise. You can do it wrong. (You can can wrong?) Most of the time, if you do it wrong, you end up with spoilage you can see, smell, or taste.

Perceptible Signs of Spoilage

There are a bunch of different things that both want to eat your food and will make you sick. (Besides your kids.) When we talk about risks in home canning, though, we usually talk about botulism, and we’ll get to that. First, though, the easier things. Most of the time if something is growing in your food, it’s detectable.

Bad jars may have visible mold or yeast. They may come unsealed because the growing things inside build up pressure. Or the food inside may look, feel, smell, or taste off. So, most foodborne pathogens can be detected, and illness prevented with a few rules. Perceptible signs include flat sour, which is spoilage because the food is unpleasant, not because it’s toxic.

Don’t eat it if:

Imperceptible Spoilage

There are two organisms that can cause foodborne illness and never be detected by these rules. They both belong to the same genus, Clostridium. Specifically, they are C. perfringens and C. botulinum.

Neither of these is a danger with high-acid food. Even if the spores are present, they will not germinate, the bacteria will not grow, and the food will not be spoiled. This is why the controversy is centered around low-acid foods.

C. perfringens

In order for C. perfringens to cause illness because of canned food, all of these things must be true:

  1. it must be in a low-acid preparation, and its spores must survive the canning process.
  2. it must have access to oxygen, so the jar needs to be opened.
  3. it must be allowed to multiply at temperatures in the “danger zone” between 40 and 140°F.
  4. it must not be heated after it’s been allowed to multiply. (Boiling for 10 minutes will kill it.)

So, C. perfringens can absolutely make you sick, but you must make multiple mistakes for it to happen. In fact, in the U.S., you’re more likely to get food poisoning from C. perfringens at an improperly maintained buffet than from (improper cooling and holding). Also, while not mild, the illness is less severe than botulism. C. perfringens will make you violently ill, possibly for days, and is dangerous to individuals with underlying health conditions.

C. botulinum

The related C. botulinum does not require so many errors. In order for C. botulinum to cause illness, all of these things must be true:

  1. it must be in a low-acid preparation, and its spores must survive the canning process.
  2. it must not be heated before consuming it. (Boiling for 10 minutes will neutralize the toxin.)

The differences here are stark. Both of these bacteria are spore-forming: in hostile environments they form protective spores to survive. They stay dormant in that spore state until the environment is right for them to grow and reproduce. The biggest issue is that C. botulinum grows anaerobically (without oxygen). So they can grow and reproduce in low-acid food while it is stored, before it’s opened. The toxin that makes you sick is a byproduct of the bacteria’s growth. So if they’ve been growing, the toxin is present. And extraordinarily small amounts of it are needed to make you sick. (see Botulism Facts for more information and citations)

Another difference is the severity of the illness. Botulism toxin is a neurotoxin that causes paralysis. It can be treated with modern medicine, including an antitoxin and ventilators, and because of that it is much less deadly now than it used to be. Historically, 50–60% of people infected died. With modern medicine, the range is 5–10%. (see Botulism Facts for more information and citations)

How the Rebels Are Right (Risk Is Rare)

Lastly, and here is where the controversy really heats up. It’s exceedingly rare. So, those who claim that there’s way too much hype and fear about botulism have the statistics on their side. In the U.S., there are an average of 0–3 deaths due to botulism from home canning per year. Yep. 0–3. Out of about 340 million people. So, it’s literally less than one in a million. . (see Botulism Facts for more information and citations)

So, you Rebels are 100% correct to point out the risks of getting botulism are really, really, really (really) ridiculously small.

How the BtB Folks Are Right (Why Guidance Matters)

Before the widespread use of pressure canning, USDA guidance recommending pressure canning, and the discovery of the ability of C. botulinum to survive for hours at boiling temperatures, there were more cases of botulism in the U.S. It was still really small, but dozens of outbreaks a year were attributed to home canning in the U.S. in the 1910s and 1920s. Now we have about 3.5 times the population, so a return to that kind of prevalence of botulism would not be good.

The toxin’s potency is kind of crazy; a tiny bit will make you very, very ill. And while you have a 95% chance of not dying with quick diagnosis and modern treatment, you still have a 5% chance of dying. That’s very high. Also, even if you survive, you’re likely to be very, very ill for many months. So, granted, the risk of getting it is vanishingly small. But the consequences of the illness are massive.

Last, and possibly most important, following the guidelines is easy. Yes, you have to research recipes, volumes, canning times, etc., but you’re doing that anyway. Pressure canning takes less time, and with an electric canner, much less active attention.

My Take (Follow the Guidelines) - It's Easy

It’s just as easy to can according to theUSDA home canning guidelines, so I do it.

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