How to Cook Black Beans to Remove Toxins
Will we get sick if I don’t boil black beans for 20 minutes?
I was wondering if you could shed some light on cooking dried black (turtle) beans?
I have read up on your site about them, and they seem the same as the other beans I’ve cooked. But the ones I bought came with a little flyer to say they need to be boiled for at least 20 minutes to remove toxins that can make you ill…?
I thought it was only kidney beans that needed hard boiling to remove toxins. I don’t want to do something wrong and make us all sick! – Natasha P.
Savvy Vegetarian Advice:
Hi Natasha, I don’t think that you need to boil black beans for 20 minutes.
I’ve been cooking black beans for many years and have never gotten sick. But they do need long soaking (12 hours) with a rinse or two. That alone releases toxins.
Then after draining and rinsing, bring the beans to a boil and skim the foam before covering and simmering until tender.
The beans will stay at boiling point for long enough that you will meet the minimum boiling recommendations.
Here’s a quote from an article on black beans & toxins by Bridget Coila, who seems knowledgeable and provides references:
“All legumes, including black beans, contain a compound called phytohenagglutinin, which can be toxic in high amounts. This is a major concern with red kidney beans, which contain such high levels of this compound that the raw or undercooked beans may be toxic when consumed. However, the amount of phytohenagglutinin in black beans is typically much lower than the levels in kidney beans, and reports of toxicity have not been linked to this type of bean.
“If you still have concerns about phytohenagglutinin, cooking beans thoroughly breaks down the toxin and lowers the levels in the beans. The U.S. Food and Drug Administration recommends boiling beans for a minimum of 10 minutes before consuming them. The FDA recommends against cooking dried beans in a slow cooker because these devices typically cook food at temperatures that do not break down phytohenagglutinin and may actually raise the levels of this toxin.”
Here is more info on beans and toxicity from Wikipedia:
“The toxic compound phytohaemagglutinin, a lectin, is present in many common bean varieties, but is especially concentrated in red kidney beans. White kidney beans contain about a third as much toxin as the red variety; broad beans (Vicia faba) contain 5 to 10% as much as red kidney beans.”
“Phytohaemagglutinin can be deactivated by boiling beans for ten minutes; the ten minutes at boiling point (100 °C (212 °F)) are sufficient to degrade the toxin, but not to cook the beans. For dry beans, the U.S. Food and Drug Administration (FDA) also recommends an initial soak of at least 5 hours in water which should then be discarded.”
“If the beans are cooked at a temperature below boiling (without a preliminary boil), as in a slow cooker, the toxic effect of haemagglutinin is increased: beans cooked at 80 °C (176 °F) are reported to be up to five times as toxic as raw beans. Outbreaks of poisoning have been associated with cooking kidney beans in slow cookers.”
“The primary symptoms of phytohaemagglutinin poisoning are nausea, vomiting, and diarrhea. Onset is from one to three hours after consumption of improperly prepared beans, and symptoms typically resolve within a few hours. Consumption of as few as four or five raw, soaked kidney beans can cause symptoms.”
“Beans are high in purines, which are metabolized to uric acid. Uric acid is not a toxin as such, but may promote the development or exacerbation of gout. For this reason, people with gout are often advised to limit their consumption of beans.”
I slow cooked beans for many years (including kidney beans), but I always soaked them, and brought them to a full rolling boil before adding them to the slow cooker. My family never got sick, but maybe we were just lucky.
For the last couple of years, I’ve been cooking all beans in a pressure cooker, which maintains a cooking temperature well above boiling for the cooking time and during the slow pressure release time. Pressure cooking also greatly shortens cooking time.