Botulism in the news

Just as the safety of the food supply is coming under increased scrutiny we have the Castleberry Foods botulism recall, now involving a variety of brands of Hot Dog Chili Sauce and dog foods. Both have something in common you wouldn't necessarily think of at first (unless you knew about botulism). Both chili sauce, which you put on your cooked hot dog just before eating, and dog food are eaten by their respective consumers without further cooking. This is characteristic of foodborne botulism because the botulism toxin, one of the most deadly and potent toxins known, is also heat labile. Heating it up for just a few minutes is sufficient to inactivate the poison. This is the explanation for why botulism frequently involves home canned condiments, vegetables or cold soups. How hot do you have to heat it? The CIDRAP site gives 85^o C. (that's 185^o F.) but also recommends boiling for 15 minutes to be safe. That's a pretty big difference and a huge safety factor, but botulism can be a pretty deadly disease. There are stories of people opening a jar of preserved vegetables, taking a small taste because the contents seemed a bit "off," and dying from botulism. The toxin is that potent.

Botulism isn't an infection from the botulism organism. It is an intoxication from the toxin the botulism organism produces in the food before you eat it. The botulism organism can only grow in airless environments, which explains why they are often found in improperly canned foods. The toxin producing bug is ubiquitous and forms extremely hardy and resistant spores when it finds itself in an unfavorable environment (too dry, too hot, too acid). These spores are resistant to temperatures as hot as boiling water. If you want to kill a botulism spore you have to heat it above boiling for a significant period of time. For foods with a significant amount of liquid, that requires cooking them under pressure because at atmospheric pressure you can't heat water above boiling. So you need to use a pressure cooker and you need to have the coolest part of the food at least hot enough and long enough to inactivate the very resistant spore form. So when people "put up" food they need to be sure they have killed the spores. To properly can your greenbeans at home you would need to put a thermocouple or thermometer into the part of the jar or can that is heated least and last and then wait for it to get to a high enough temperature for long enough. Obviously the average person can't and doesn't do this. Instead they rely on others to do it for them and put the results in a chart so you can just look it up (one example here).

Note that the botulism problem is usually involves only low acid foods. Once the botulism spore finds itself in an airless environment of the right temperature (say somewhere between 50 ^o F./ and 120^o F.) it can germinate, but if the surround is too acid (say below pH 4) it won't grow and won't produce toxin. That still leaves a huge variety of canned vegetables, fermented, smoked and canned fish and who knows what else. Even commercial carrot juice has been a vehicle for botulism. Despite this, it is not very common. In the US there are a couple of dozen foodborne cases a year (you can get botulism toxin syndrome other ways, for example, too much Botox, which is just botulinum toxin used therapeutically; this is an example of iatrogenic botulism).

There are lots of good botulism resources on the web. This is CIDRAP's excellent contribution and another good one from eMedicine.

Good old home cooking with locally grown and prepared foods is one of the best ways to eat safely. In general. But in the case of botulism this isn't the case. Almost all botulism cases are from home canned foods. Botulism like the Castleberry case from commercially canned foods is rare, although it does occur. Like all things, the mantra of locally grown, home prepared is safest isn't always right. On rare occasions it can be dead wrong. So don't just assume that home cooking is safe. Home cooking still has to be done properly.

Just a word to the wise.

Update (hat tip Edna): Many more Castleberry recalls here.