Monday, September 24, 2007

Undercooked Beans Can Be Toxic

If you find yourself in a hurry, and tempted to cook beans "al dente" (just a tad bit too firm)...don't!

Time or fuel constraints might tempt some to settle for slightly undercooked beans. Did you know that dried Kidney beans (and other beans) that are not thoroughly cooked can cause poisoning? This can range from moderate to severe discomfort.

Hat-tip to Science Teacher (at, for this link: FDA/CFSA

The toxin is called: "Phytohaemagglutinin"

"The onset time from consumption of raw or undercooked kidney beans to symptoms varies from between 1 to 3 hours. Onset is usually marked by extreme nausea, followed by vomiting, which may be very severe. Diarrhea develops somewhat later (from one to a few hours), and some persons report abdominal pain. Some persons have been hospitalized, but recovery is usually rapid (3 - 4 h after onset of symptoms) and spontaneous." snip

Alan T. Hagan, a CE poster who is also a food storage and preservation expert, said: "Most of the common beans are Phaseolus vulgaris so they all contain varying levels of this compound.... Virtually all legume seeds contain various compounds that are anti-nutritional which is why they must be cooked before eating them...."

5. Associated Foods: 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 (176 degrees F.) 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.

6. Relative Frequency of Disease: This syndrome has occurred in the United Kingdom with some regularity. Seven outbreaks occurred in the U.K. between 1976 and 1979 and were reviewed (Noah et al. 1980. Br. Med. J. 19 July, 236-7). Two more incidents were reported by Public Health Laboratory Services (PHLS), Colindale, U.K. in the summer of 1988. Reports of this syndrome in the United States are anecdotal and have not been formally published.

AT Hagan also said, in response to another poster who was concerned about the sometimes kinda crunchy commercially canned beans:

"Canned beans have been cooked well over 176 degrees Fahrenheit. Cook your beans until they are not crunchy and you'll be fine. Other than relatively small amounts of bean sprouts (usually not made with P. vulgaris varieties) don't eat raw legumes. They need to be cooked."

Another poster, Summerthyme, pointed out that this temperature issue with the beans "...might be a bigger issue with people grinding dry beans for "bean flour" and then using it as a thickener in various dishes, possibly without thorough cooking..."

Here's the link to that thread:

So, to sum it all up: If you want to cook beans using a low temperature method, first boil the beans, or bean flour for 10 minutes to destroy the toxin. If you have cooked the beans the conventional way, and if you can't mash a bean between two spoons, it needs to be cooked longer.

I make my own "bean powder" by dehydrating cooked beans, then pulverizing them to a powder for thickening and adding extra nutrition to soups, stews and such.

Beans and rice are a staple in many emergency food storage plans. Together, they make an nutritious protein-rich meal, and store well for a long time.

No comments: