Not boiling dried kidney beans increases toxicity?

A friend sent me this Wikipedia link about cooking dried kidney beans in the slow cooker:

It basically says that if you don't boil your dried beans for 10 mins first but just throw them in the crock, it increases their toxicity.

Is this true? Has anyone ever heard this?

  • Posted by: jenmmcd
  • February 6, 2012


jenmmcd February 6, 2012
Wow... I guess I never believe something until F52'ers confirm it. And I'm bummed b/c I just got a cookbook about cooking Indian in the crock and many of the yummiest recipes have kidney beans in them. Guess I'll be cooking them for a bit first...
Cody,Buchholz February 6, 2012
That doesn't mean you can't use presoaked canned kidney beans.
boulangere February 6, 2012
Yes, it is true. It is recommended that dried red kidney be soaked for at least 5 hours, then the water drained and the beans rinsed. Alternatively, they should be first rinsed, then boiled for at least 10 minutes before any further cooking.

This is from the FDA website:

Phytohaemagglutinin, the presumed toxic agent, is found in many species of beans, but it is in highest concentration in red kidney beans (Phaseolus vulgaris). The unit of toxin measure is the hemagglutinating unit (hau). Raw kidney beans contain from 20,000 to 70,000 hau, while fully cooked beans contain from 200 to 400 hau. White kidney beans, another variety of Phaseolus vulgaris, contain about one-third the amount of toxin as the red variety; broad beans (Vicia faba) contain 5 to 10% the amount that red kidney beans contain.

The syndrome is usually caused by the ingestion of raw, soaked kidney beans, either alone or in salads or casseroles. As few as four or five raw beans can trigger symptoms. Several outbreaks have been associated with "slow cookers" or crock pots, or in casseroles which had not reached a high enough internal temperature to destroy the glycoprotein lectin. It has been shown that heating to 80°C may potentiate the toxicity five-fold, so that these beans are more toxic than if eaten raw. In studies of casseroles cooked in slow cookers, internal temperatures often did not exceed 75°C.

SKK February 6, 2012
I read the footnote from the FDA, so the research appears to be sound. Don't have a slow cooker, and if I did I would definitely boil the kidney beans first as directed. White kidney beans (cannelini) don't have the same level of toxicity.
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