Bean seeds come in a wide range of colors and sizes. Photo: cooperroadcsa.blogspot.com
Question: I was a bit slow harvesting my green and yellow beans this summer and many dried out and went to seed. I’ll use some as seeds for next year’s crop, but since I have a lot of them, I wondered if the seeds were edible.
Answer: Yes, the dry seeds of the common bean (Phaseolus vulgaris) are edible. In fact, they have been used for thousands of years for soups, chilies, stews, etc. Boston baked beans, a classic dish I’m sure you’ve eaten many times, are, in fact, made from dry beans.
That said, it’s important to prepare dry beans properly, including soaking them in water for at least 5 hours (discard the water used to soak them) before boiling them for at least 15–20 minutes (the US FDA recommends 30 minutes).
This is because the dry seeds of all types of common bean contain phytohemagglutinin (PHA), a toxin that is destroyed by prolonged cooking. It’s not all that rare that people end up in the hospital after consuming soaked beans that they thought were cooked. Interestingly, rats seem to know dry beans are poisonous, as they will raid stores of cereals and other crops, but never touch dry beans.
The level of phytohemagglutinin varies considerably from one type of bean to another and it is generally quite low in beans harvested from green and yellow beans, but very high in kidney beans, both red and white. Even so, proper soaking and cooking are recommended for all beans, regardless of the color of the seed.