Radishes, baking soda... pretty colors?

I need a chemist on this one, it's kinda weird. I just started cleaning some radishes for use in egg salad, and I like to use baking soda when I clean roots so I can get all the dirt out of the crevices. Well, as soon as baking soda hits the radish, it turns bright purple! The only time I've seen purple like that on my fingers is after handling certain traditional face masks of Bedouin women... yeah, long story. They're made of fabric, but some process is applied to make it seem like the cloth is overlaid with gold. But really, my question is... why did my radish go all purple on me? Anyone have any clues? Because a cursory googling got me nowhere, and I'm not exactly well up on chemistry. :-/

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5 Comments

BerryBaby
BerryBaby March 5, 2019
Things like this happen and I think 'chemical reaction'. First time it happened to me was with purple Bell Peppers. As soon as they hit the heat, they turned green! Had no idea that would happen so only use them raw in salads. It's a forever cooking, learning, experience.
 
HalfPint
HalfPint March 4, 2019
Disclaimer: I only have a Bachelor of Science in chemistry and was a R&D chemist for about 8 years.

From what I've read in some of the science and botany literature. The pigmentation of radishes comes from a class of compounds called "Anthocyanins". As you found by washing with baking soda, the colors can be affected by pH changes. Anthocyanins are also found in berries, black beans, etc, even autumn leaves. They are also anti-oxidants which makes them quite healthy to consume.
 
sweetlime
sweetlime March 4, 2019
I don't know about the radishes, but the face masks you're talking about are dyed with natural live indigo. Its called nil in arabic. The cloth is dyed very heavily and coated with powdered indigo, rather than in a liquid solution like shibori, I think, and that is why the fabric is stiff with it, why it rubs off on fingers and body, and the gold sheen. The kind I know rubs off more bluish than purple radishy, though maybe that is in the eye of the beholder.
Are you in Oman by any chance?
 
Lori T.
Lori T. March 4, 2019
Somewhat technically/chemically speaking-the pigment which gives red radishes or red/purple veggies are anthocyanins which react to pH changes. When exposed to a base ingredient- like baking soda, they turn purple to blue as the pH goes up. They are most stable in acidic, like vinegar solutions.
 
C S.
C S. March 4, 2019
Baking soda is basic, and many reddish pigments in foods react to that by turning purple. If you take a purple cabbage and put baking soda on it it will turn more bluish purple while if you put vinegar on it (acid) it will turn brighter red. I did not know this was true of radishes but it does not surprise me.
 
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