The Motley Fool Discussion Boards

Previous Page

Food & Drink / Vegetarian and Vegan Fools


Subject:  Re: Delicious Cuban black beans recipe Date:  9/13/2012  12:47 PM
Author:  zoningfool Number:  5429 of 5869

Juat so you's not a good idea to use a slow-cooker to cook beans or legumes in the manner described in the link. Specific steps need to be taken first--primarily soaking overnight, rinsing, then boiling vigorously before adding to a slow-cooker:


This compound, a lectin or hemagglutinin, has been used by immunologists for years to trigger DNA synthesis in T lymphocytes, and more recently, to activate latent human immunodeficiency virus type 1 (HIV-1, AIDS virus) from human peripheral lymphocytes. Besides inducing mitosis, lectins are known for their ability to agglutinate many mammalian red blood cell types, alter cell membrane transport systems, alter cell permeability to proteins, and generally interfere with cellular metabolism....

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.

Lectins in Dry Legumes

The Issue

Lectins are naturally-occurring plant proteins that are found at low levels in the edible parts of commonly consumed fruits and vegetables such as apples, bananas, cucumbers and sweet peppers, and in varying levels in many types of legumes including soybeans, lentils, lima beans and kidney beans.

Lectins, also called haemagglutinins, are toxic to humans if consumed in large amounts. Canadians are rarely exposed to levels of lectins that cause serious health effects. However, there are occasional reports of short-term adverse symptoms, most commonly associated with eating improperly cooked red kidney beans. Uncooked and improperly cooked red kidney beans can contain elevated levels of a certain lectin, phytohaemagglutinin, relative to other types of legumes....

...The proper preparation of dry red kidney beans and other dried legumes can reduce the potential for foodborne illness...

Note: Slow cookers and crock pots do not reach sufficiently high temperatures to destroy lectins, and therefore should not be used...

More info here:

Copyright 1996-2018 trademark and the "Fool" logo is a trademark of The Motley Fool, Inc. Contact Us