I have to publish my first major retraction today. I cant believe I didnt know about this before, but…do NOT follow my old slow cooker beans technique when cooking beans, especially kidney beans, cannelini beans, or broad beans.
Red kidney beans contain high levels of a toxin that occurs naturally in beans, Phytohaemagglutinin (also known as Kidney Bean Lectin.) If raw or undercooked red kidney beans are eaten…well, bad things happen. Lets just say youll be getting to know the pattern of tiles in your bathroom very well.For all the gory details, check here.
With normal cooking, this isnt a problem. The toxin is destroyed after ten minutes of boiling (cooking at 212*F or 100*C.), and most stovetop recipes easily take care of the toxin with their hours of simmering at that temperature. Raw, soaked beans are bad; eating four of them is enough to cause symptoms. Now, heres the problem with slow cookers: undercooked beans (cooked at 80*C, roughly 170*F) increase the toxicity fivefold. And, most slow cookers have their “low” setting at about 180*F. If your slow cooker runs a little cooler than most… England tracks this more carefully than we do here in the US. They had seven outbreaks of kidney bean poisoning between 1976 and 1979, caused by raw, soaked kidney beans or kidney beans cooked in a slow cooker.
The toxin occurs in red kidney beans, and to a lesser extent in white kidney beans (cannellini beans) and broad beans. Other beans contain the toxin, but at much lower levels.
How did I miss this? I never had, um, gastrointestinal issues from slow cooked kidney beans. My slow cookers must run hot enough that the toxin was destroyed. Also, I prefer black or pinto beans to kidney beans, so those are the beans Im usually slow cooking. In the future, I am always going to boil my beans for at least 10 minutes before cooking them in a slow cooker. This takes some of the simplicity out of the “dump and cook” technique that I use, but its still pretty simple. And the alternative is not pretty.
I want to extend my sincere apologies to anyone who followed my technique. I hope I didnt cause you any…problems.
Update 2016-01-15: Since I was asked…whats my solution to this problem? I switched to using a pressure cooker to cook dried beans.
Update 2015-12-16 and 2017-09-22: I closed comments on this post. They keep turning into denial and name calling.
To sum up: Saying: “This hasnt happened to me, therefore it doesnt exist” is faulty logic.
If it hasnt happened to you, great! You got lucky, and I hope your slow cooker keeps running hot enough.
Studies have found slow cookers do not reach a high enough temperature to destroy the harmful bacteria in undercooked beans. The PHA toxin is destroyed at 212°F when cooked for at least 10 minutes. Beans prepared in a slow cooker often only reach an internal temperature of 167°F. How will I know if I get sick?
Update 2016-01-15: Since I was asked…whats my solution to this problem? I switched to using a pressure cooker to cook dried beans.
How did I miss this? I never had, um, gastrointestinal issues from slow cooked kidney beans. My slow cookers must run hot enough that the toxin was destroyed. Also, I prefer black or pinto beans to kidney beans, so those are the beans Im usually slow cooking. In the future, I am always going to boil my beans for at least 10 minutes before cooking them in a slow cooker. This takes some of the simplicity out of the “dump and cook” technique that I use, but its still pretty simple. And the alternative is not pretty.
If it hasnt happened to you, great! You got lucky, and I hope your slow cooker keeps running hot enough.
The toxin occurs in red kidney beans, and to a lesser extent in white kidney beans (cannellini beans) and broad beans. Other beans contain the toxin, but at much lower levels.
Red kidney beans contain high levels of a toxin that occurs naturally in beans, Phytohaemagglutinin (also known as Kidney Bean Lectin.) If raw or undercooked red kidney beans are eaten…well, bad things happen. Lets just say youll be getting to know the pattern of tiles in your bathroom very well.For all the gory details, check here.
Weeks ago, I saw something about the dangers of cooking beans in a slow cooker. I don’t recall where information came from, the particulars, or how reliable the source might have been. All that stayed with me were the words “danger“, “beans“, and “slow cooker.”
Is it safe to cook beans in a slow cooker? It’s not an issue I confront every day. However, when I cook beans, I want to do it safely.
Cooking the beans properly destroys the toxin. Soaking and then boiling the beans for at least 10 minutes (some authorities – including the FDA’s Bad Bug Book (Seriously – that’s the name of the publication. Don’t you love it!) – suggest boiling for at least 30 minutes) will eliminate the toxin.
The only way for me to ever cook another bean in a slow cooker without worrying that I would poison someone was to find out the facts. Here is what I discovered about whether it is safe to cook beans in a slow cooker:
This precaution is most important for red kidney beans, but also applies to white ones. The latter are sometimes called cannellini beans. Red kidney beans contain about 3 times as much of the toxic agent as the white ones. However, white kidney beans can also cause illness if not fully cooked. I’ve also seen cautions about raw or undercooked soy beans (which contain a different toxin, called a trypsin inhibitor, which is also destroyed with the same type of proper boiling/cooking), but I rarely see recipes that call for cooking raw soy beans.
Why You Should Absolutely Never Cook Raw Beans In A Slow Cooker
FAQ
Why can’t you cook kidney beans in a slow cooker?
What are the symptoms of kidney bean poisoning?
Why are my beans still hard after slow cooking?