Contain relatively high amounts of phytohemagglutinin, and thus are more toxic than most other bean varieties if not pre-soaked and subsequently heated to the boiling point for at least 10 minutes. The US Food and Drug Administration recommends boiling for 30 minutes to ensure they reach a sufficient temperature long enough to completely destroy the toxin.[2] Cooking at the lower temperature of 80 °C (176 °F), such as in a slow cooker, can increase this danger and raise the toxin concentration up to fivefold. Canned red kidney beans, though, are safe to use immediately, as they are cooked beforehand.
https://en.wikipedia.org/wiki/Kidney_bean
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