In early July, I found a package of these remarkable beans in my barn. “Is it too late to plant them?” I wondered. I decided to plant them and see. In less than two weeks, seedlings were poking up through the soil in neat rows. By mid-August, purples beans hung from plants with bright green, heart-shaped leaves. Magic.
In late August, I walked out to the garden to harvest my magic beans. As I walked back to the house I thought about the beans and their second magic trick. In the kitchen, I washed the purple beans, put them in a bamboo steamer and turned up the heat. When they were done cooking, I turned off the stove, opened the steamer, and placed the now-green beans on a plate. Magic.
My daughter feels like she is in on a big secret when she plants, picks, and cooks purple beans. We happened upon this transformation trick by accident. Aurora was five years old, loved all things purple, and liked to eat green beans with soy sauce. When we discovered purple beans, we had to plant them. The first time we cooked, them I was surprised when I opened the pot and found bright green beans. I suspected it had something to do with chlorophyll and heat, but I didn’t know for sure.
I have since learned that purple beans get their color from pigment called anthocyanins. Anthocyanins is responsible for the purple, reddish range of colors. When the beans are heated, the surface molecules break apart and expose the chlorophyll underneath. Chlorophyll is green.
In the fall, nature plays the reverse trick with the leaves on trees. During the growing season, chlorophyll is continually produced and broken down, produced and broken down. This process gives leaves a green appearance. As the nights grow colder and the days get shorter, the sugars in the trees stop running. The lack of sugar means chlorophyll productions stops and the existing chlorophyll breaks down to reveal the pigments—carotenoids and anthocyanins. Carotenoids range in color from pale yellow through bright orange to deep red. Bright reds to purples come from anthocyanins.
Next spring or summer, if you get a late start, consider planting purple beans in your garden and grow your own magic!