I ate some cooked artichoke stems; some of the outermost skin is tough, so I just chewed it and then spit out the inedible bits. I left those bits in a container on my kitchen counter near the sink, still sealed. A day later, when I dumped the contents, the leftover bits were a bright blue color. What does this mean? Something with saliva enzymes?

  • 5
    We most certainly want to see a picture! If only out of curiosity.
    – Stephie
    Jan 27, 2017 at 18:30
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    Artichokes can have a bit of a purple tinge .. and there are purple-ish food items that will go blue in the presence of alkali. I wouldn't be surprised if that was it. see kitchenpantryscientist.com/…
    – Joe
    Jan 27, 2017 at 19:24
  • Do you salt the artichoke stems at all? Is your salt iodized? Perhaps chewing the stems breaks the outer coating and releases starches, that interact with iodized salt. Just a stab in the dark..... May 30, 2017 at 14:42
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    related? : cooking.stackexchange.com/q/40616/67
    – Joe
    Sep 8, 2017 at 1:23

3 Answers 3


We eat artichoke often. We pressure cook them in an old one quart aluminum pot. I have seen the cut stem (not chewed) butt turn and ooze blue from the cut stem when left in the fridge too long. In that condition the stem has a sour fermentation, but no obvious mold. I have eaten it like this thinking, I am getting extra. I like artichoke stem a lot and have bought them with long stem in Oregon, USA. The blue appears to be in the nature inherent with the thistle flower that it is.


I was a chemistry major in college and I suspect this happened because the copper in the artichoke reacted with oxygen in the air creating copper oxide, which is a really pretty blue color in low concentrations. You chewing it may have broken it up, allowing the oxygen easier "access" to react with the copper when you left it out.


It should be a reaction to certain metals, typically iron or aluminum. Not sure why artichoke + iron = blue, but that seems to be how it works.

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