My mother pickled a bunch of garlic recently and it turned blue soon after. She has had this happen once or twice before where some turned green, but this time all of them turned really blue.

I tried Googling it, but only found mentions of it being a chemical reaction (that much is obvious) and mostly just speculation as to the causes and prevention, but little discussion on the safety of blue/green garlic. There are a couple of of question here about cooked / old garlic and onions turning green, but they have the same information as the other pages.

The few mentions of safety that I can find only go so far as to say that “it’s safe”—we assumed as much when we didn’t die after eating some last time—but they do not give any sort of explanation or proof to that effect. Chemical reactions are by definition change, which means that something that was safe can become not so.

Does anyone know of any information as to the safety of blue/green garlic (particularly pickled) that expounds on “it’s safe”, perhaps with some sort of test or experiment?

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Since it was pickled, I believe it was a reaction with the vinegar causing it to turn green. Harold McGee has a good article on the very issue. He also goes into some detail in another artical here. I have heard various factors that can affect it, like the presence of dissolved metals, and the age of the garlic prior to being canned. However, I don't have any other info on those...

I do believe it's safe, assuming no other signs of spoilage are there.

  • I’ve seen talk about metals in the water, but I’m pretty sure she avoids any and all water when pickling (she has scolded me plenty of times about contaminating jars of pickled things with water, utensils, and fingers). Obviously it’s not fatal because we ate some last time and didn’t die, but safety is more than just lethality. I don’t remember now, but for all I know, we may have had digestive problems for a while after eating it, or sleep problems, headaches, etc. – Synetech Feb 18 '12 at 20:44
  • Oh, I'd be surprised if it was the metal in this case. I just mention it because that is what I have read/heard. McGee doesn't talk about metal in his articles. I believe his explaination is more relevant/correct here. – talon8 Feb 19 '12 at 4:53

The answer is anthocyanins, the same that can turn ginger blue and are responsible for purple snap beans and cabbage. The reaction occurs relative to pH and is perfectly safe. Anthocyanins are present in their range of colors in many foods including cabbage, ginger, garlic, and berries. When used as an additive, they have the E number E163.

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