Adventures in Ethics and Science

The mystery of the beans.

Earlier this week, I cooked up about a pound of the bush beans from our garden. There was a mix of yellow, green, and purple beans (although, as expected, steaming transformed the purple beans to a dark green color). I dressed the cooked beans as usual and served them with dinner.

As I was clearing the table after the meal, I saw this:

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Where did that pink liquid come from?!

None of the ingredients I used to make the beans were pink (or even red or orange). Was this a supernatural phenomenon (HAUNTED BEANS!!)?

Actually, on reflection, I came to a reasonable explanation about the source of the pink liquid. My better half tested my hypothesis before washing the bowl and found evidence to support what I think happened.

Can you explain the pink liquid?

(You can ask for more information, if you need it, in the comments.)

Comments

  1. #1 qetzal
    October 31, 2008

    Do you add vinegar to the bean salad? Perhaps one of the pigments in the beans is a natural pH indicator, changing color from green to pink/purple at low pH.

  2. #2 llewelly
    October 31, 2008

    There was a mix of yellow, green, and purple beans (although, as expected, steaming transformed the purple beans to a dark green color).

    Later:

    None of the ingredients I used to make the beans were pink (or even red or orange).

    The yellow and purple beans contain a red pigment. The beans took up water when they were steamed, the water picked up the pigment, the beans cooled, and the water leaked out.

  3. #3 chezjake
    October 31, 2008

    I’m guessing that your “dressed as usual” includes an acid, probably vinegar or lemon juice. The purple in the purple beans is due to anthocyanins (same compounds that make autumn leaves turn red and orange), and anthocyanins are also used as pH indicators, as in your red cabbage example a few eeks ago.

  4. #4 Ropty
    October 31, 2008

    I dressed the cooked beans as usual

    What was the usual way?

  5. #5 Janet D. Stemwedel
    October 31, 2008

    Y’all are good! Qetzal and chezjake pretty much nailed it.

    The purple beans, when steamed and imperfectly drained, seem to have created an indicator similar to our cabbage water indicator. Indeed, if we had chopped up the purple beans and steeped them in hot water for awhile, I suspect we’d have ended up with a faintly purple solution. (I’ll check this when we harvest more purple beans.)

    Our “usual way” of dressing steamed beans is to toss them with olive oil and lemon juice. Apparently, this is the first time we’ve dressed our purple beans this way, though.

    The lemon juice (an acid) reacted with the stealth indicator created by the purple beans and turned that indicator pink. Before cleaning the bowl, my better half sprinkled a little baking soda (a base) in the bowl, whereupon the liquid turned bluish.

    I now feel that food-based indicators are dreadfully underutilized in creating flashy color changes when foods are dressed at the table.

  6. #6 Karen
    October 31, 2008

    And here I was going to accuse you of adding pink coloration to things the same way I do occasionally, by accidentally adding a small quantity of a dark red substance liberated from a finger. :-)

  7. #7 Doug Alder
    October 31, 2008

    Well if it were pasta and not beans I’d say you had a visit from the FSM ;)

  8. #8 LP
    November 4, 2008

    This happened to me recently with asparagus (and lemon juice). Thanks for the explanation!