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Perplexing purple beans. July 17, 2011

Posted by ourfriendben in gardening, recipes.
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Silence Dogood here. Yesterday, I broke down and bought my first carton of purple string beans at our favorite Mennonite farm, James Weaver’s Meadow View Farm in scenic Bowers, PA.

Our friend Ben and I love string beans, and our very favorite way to eat them is to boil mixed green and yellow wax beans ’til just tender, drain them, toss in butter, RealSalt or Trocamare (hot seasoned salt), and lemon pepper or cracked black pepper, shake the pan, and serve. Yum!!! We can’t eat enough of them, and they reheat well, too. (Our black German shepherd, Shiloh, and Plutarch the Parrot prefer their string beans raw, but they can’t seem to get enough of them, either.)

So why have I waited so long to try purple string beans (it appears that the variety is called ‘Royal Burgundy’)? It’s because I know that the anthocyanins that give the beans their gorgeous purple color dissipate in cooking, leaving you with plain green beans. We love plain green beans, anyway, so why bother to buy purple beans just to watch them join the green beans in the pot rather than creating a gorgeous purple, green and yellow mix?

This is certainly not a phenomenon limited to beans. Purple broccoli, cauliflower, bell peppers, and asparagus also change to green when they’re cooked. (Fortunately, purple, aka “red,” cabbage and onions don’t seem to have this issue.) And since purple broccoli, cauliflower, peppers, cabbage, and onions can be eaten raw in salads, and the broccoli, peppers and cauliflower can be eaten raw with dips to add color variety to crudite plates, there are ways around the go-to-green issue. Not so with asparagus and beans. 

What to do? What if you briefly blanched, steamed, or stir-fried the beans or asparagus, then added them to boiled green and yellow wax beans or white and green asparagus? No dice, apparently; it only takes 2 minutes of cooking to turn them green.

Okay, then, what about roasting or grilling them? I’ve never tried roasting beans, but roasted tiny green asparagus, with a little olive oil drizzled on top, is incredibly delicious. Why wouldn’t roasted purple asparagus or beans be equally yummy, and without the interaction of water or steam, would the purple color stay true? I haven’t found an answer online, so I guess the only way to find out is to try it.

The two ways to keep the purple that I have found are to add the beans raw to salads or, as Lee Reich, the famous fruit expert, notes in a 2009 AP article, to soak them in vinegar or lemon juice before (briefly) cooking them. (Apparently increasing acidity helps them keep their anthocyanins and thus their purple color.) Hmmm, since we always put lemon juice on asparagus, along with butter, before serving, it might be worth trying this with purple asparagus, but lemon- or vinegar-soaked beans?! Pickled green and yellow beans are a specialty around here, so you’d think vinegared (pickled and canned) purple beans would have caught on right away if this worked. But I’ve never seen them. And adding vinegar or lemon juice to fresh-cooked beans is not something I’d really want to try.

One suggestion I found that sounds promising is to butter-baste the raw beans as quickly as possible, losing some depth of color but still having purple beans. Hmmm. I’d like to try this, and also roasting them. Or maybe stirring warmed purple beans into the boiled green and yellow wax beans we love before adding the butter and seasonings and shaking the pan would work?

If worse comes to worst and the purple beans turn green, apparently they still taste good like green string beans, so all that’s lost is the aesthetic quality. But if any of you enthusiastic gardeners and cooks out there know how to cook purple string beans and keep them purple, please check in and share your hard-won knowledge with all of us!

               ‘Til next time,




1. eric - August 24, 2011

Just fair warning Silence, raw beans can be poisonous, so I would seriously reconsider maintaining that purple hue you like. Do please cook them thoroughly. Take care!~

Thanks, eric! An important warning, especially for all the raw food folks out there…

2. eric - August 24, 2011

Perhaps I spoke too soon, as you already knew that.. oh well, stay safe, and good article!

Actually, I didn’t know that, so I’m really grateful you took the time to come online and say so. I wouldn’t eat a raw string bean because of the “hairy” texture in any case. But I will say that my dog, chickens and parrot love them and have suffered no ill effects so far!

3. Tom - February 3, 2012

Greasy bean varieties are smooth and glossy and do not have that “hairy” texture, hence the name.

It is my understanding that raw beans are “technically” poisonous but will at most cause gastronomic distress as the primary reaction in humans, unless eaten in very large quantities. I have eaten them raw right out of the garden my entire life and never had a problem.

Of course it is the responsibility of each and every person to know what they are putting in their mouths and whether it is safe of not.

My dogs also love raw beans and bark at me while I am harvesting so I will throw some to them. They won’t pick them off the plants but they will try to steal them out of the basket if I neglect to throw enough beans to them.

Thanks for the clarification, Tom! I can hardly cook when I’m preparing beans because my huge black German shepherd sits at attention immediately beside me, waiting for her favorite treat!

4. Jim - June 11, 2012

I came across this article after purchasing some purple beans at the farmer’s market yesterday. I was very disappointed when they turned green after cooking. However, I inadvertently found a way to turn them back (a little anyway). I make a green bean salad which is made by cooling the cooked beans and soaking them in lemon juice, olive oil, onions, garlic, and seasonings. After soaking the beans over night, some of the purple hue came back. Thought you might be interested.

Wow, Jim, that’s really interesting! Next time I’m lucky enough to find purple beans, I’ll experiment with this. Thanks!

5. Ray Carnes - September 11, 2012

I recieved some ornamental purple beans from a friend last year. I grew the seeds this year and they have taken over my whole porch, Climbing to the rooftop. The green leafs have purple veins. The blossems are bright purple, as are the beans. They look alot like Butter beans, or climbing lima beans, but are very fast growing after all the rain that we had. I’m not sure if they are edible or not.
They are a very beautiful purple bean pod. I have not tried to shell one yet.

6. Ray - September 11, 2012

The beans that I have the good fortune to aquire are purple before plucking off the vine. The dark green leaves have purple veins and the blossoms are also purple, but a lighter shade, Being the bean pods are so much more, a deeper dark purple.

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