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Mar 17, 2001 06:09 AM

Anyone ever had garlic turn blue-green while cooking?

  • k

This happened while I was sauteeing veal last night. I had garlic, veal, capers and artichokes in the pan, and immediately after I added a bit of white wine and lemon, the garlic turned bright blue-green! We ate it anyway and it tasted fine, so it couldn't have been harmful. (after cooking a while longer, the color started to fade a bit) I have never seen this happen in restaurants, and I am sure I have eaten dishes with the same ingredients. What went wrong?

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  1. I've never seen what you describe, but I assume the garlic was reacting with something else in the pan or the pan itself. I do remember seeing a reaction like this a long time ago and if I had paid more attention to high school chemistry I might be able to give you an idea of what the reaction was. I guess the next step would be to try to recreate the effect. Try doing it with another clove from the same head to garlic. If it happens again try using a different head of garlic. If it doesn't happen with the second head at least you'll know it was the garlic. You could keep changing one item at a time (a different pan, different butter, etc.) until you find out which is the culprit. Happy experimenting!

    6 Replies
    1. re: Deven Black

      Why Does Garlic Turn Blue and Is Blue Garlic Safe To Eat?
      :The colors occur when enzymes and amino acids present in garlic react with the sulfur compounds responsible for garlic’s pungent smell. The reaction causes different multipyrrole molecules to form. Different types of multipyrrole molecules are responsible for the different pigments. The multipyrrole molecule most familiar to us is chlorophyll, produced by plants in the presence of light; however, chlorophyll is not produced by the cooking or pickling processes that turn garlic blue."

      My pickled garlic turned a pale greenish-blue color. What's wrong?
      "According to the Food Network at looked into the reason pickled garlic sometimes turns blue or green. Garlic contains anthocyanins, water-soluble pigments that turn blue, green or purple in an acid solution. While this color transformation tends to occur more often with immature garlic, it can differ among cloves within the same head of garlic. The garlic flavor remains unchanged, and it totally edible without bodily harm."

      1. re: maria lorraine

        Hi Maria, is the older or younger garlic more prone to turning blueish? My research of the internet proves controversial, I experimented with younger and older garlic and the older one always gets blue, but not the younger one. This seems to contradict with what you mention about the amount of isoaliin is higher in younger garlic and thus it having more potential for turning blue...

        1. re: AnnaLFC

          I don't have a definitive answer, nor do I think that the Food Network'c comment that the color change occurs most often with immature garlic is absolutely accurate.

          The color change is due to thiosulfinates.
          Those are formed when cysteine sulfoxides present in raw garlic combine with the enzyme allinase, which is released when garlic is cut, chopped or crushed.

          Those thiosulfinates react with a variety of amino acids to form blue and green colors.

          From my reading, I sense a color change is more likely to occur when both onion and garlic are used, perhaps because both onion and garlic supply the precursor sulfur compounds that form thiosulfinates.

          The presence or concentration of those sulfur compounds may vary by individual variety of garlic or onion (some varieties have more) or with growing conditions (soil, amendments, etc.)

          Or those sulfur compounds may increase with the age of the garlic or onion. I don't know.

          Then again, amino acids react with the thiosulfinates to form the blue-green colors. Check out the difference in color that results depending on which amino acid is present.

          So the blue-green color might be due more to
          amino acids present (see the caption on the photo) than the thiosulfinates. In that case, what causes individual amino acids to be in the garlic or onion? I don't know.

          Read more about Allium Chemistry and the blue-green color change here:

          and here:

        2. re: maria lorraine

          Does this also apply to eggplant? I cooked some Asian eggplant last night, and it turned into this dark, bluish green this morning. This has never happened to me before. I am thinking of tossing it out.

          1. re: Ystewart

            No, eggplant turns blue for a different reason.

            The purple color of eggplant's skin is due to anthocyanin, which also is the reason for the purple color in red cabbage. That purple anthocyanin turns blue or green when alkaline ingredients like baking soda or baking powder are added to the dish or to the sauce. The color change, if not immediate, is probably due to the eggplant sitting overnight with the alkaline ingredients.

            What was your exact recipe and procedure for your eggplant dish?

            If it tastes OK to you, and you want to eat it, it won't hurt you, but I understand being skeeved by off-colors.

            1. re: maria lorraine

              Thank you, Maria! That explains it! It was coated in a tempura batter that contained baking soda!

      2. This question is popping up all over the place lately. I would have guessed a reaction with the metal too, but this is not so.

        This is the most commonly asked garlic question at UC Davis extension

        "Why did my garlic turn blue?

        The answer is: Garlic contains anthocyanins, water-soluble pigments that can turn blue or purple under acidic conditions. This is a variable phenomenon that is more pronounced for immature garlic but can differ among cloves within a single head of garlic. If you grow your own garlic, be sure to mature it at room temperature for a couple of weeks before using it.


        3 Replies
        1. re: Anne H.

          Thanks so much for the info! It must have been the acidity caused by adding the lemon and wine.

          1. re: Anne H.

            I understand the science being cited, but I've been cooking with garlic in this way for a while and haven't noticed the garlic routinely turning blue until recently. I'm cooking in anodized aluminum which is new for me. Could the metal make a difference? Is bulk garlic being treated differently than before? (Irradiated)

            1. re: Anne H.

              That's not correct, sorry. It's not an acid-based (as in lemon juice) reaction.

              The reaction is due to a defense mechanism -- an enzyme -- that is released in the garlic when it is chopped. It reacts with sulfur compounds and amino acids in the garlic, and turns blue. The blue compound is isoalliin, and there is more potential for it in young garlic, the reason garlic bulbs are often stored for two weeks before going to market.

              Here's the scientific notation:
              "The discoloration is due to pigments that form between sulfur compounds in garlic and amino acids. When the garlic tissue is disrupted, as happens in processing, an enzyme is liberated and reacts with it to form thiosulfinates compounds that then react with the natural amino acids in the garlic to form blue pigments. The age of garlic determines how much isoalliin there is in the first place, and the nature of the processing determines how much enzyme is liberated."

              Identification of Two Novel Pigment Precursors and a Reddish-Purple Pigment Involved in the Blue-Green Discoloration of Onion and Garlic, Journal of Agricultural and Food Chemistry, 2006, 54 (3), pp 843–847 DOI: Publication Date (Web): January 12, 2006.

            2. c
              Caitlin Wheeler

              Anne H. is probably right, since she has scientific evidence to back up her claim, but I did notice after cooking artichokes the other day (plain, boiled with mayonnaise, no garlic) that the leaves turned blue green after a couple of days (I'm a lazy dishwasher) Maybe it's related?

              1 Reply
              1. re: Caitlin Wheeler

                Two days of unwashed mayo and artichokes? No offense, but I think what you experienced is called "mold."

              2. I've had it happen, freaky at first sight, but fine. I've also have sunflower seeds in baked goods turn green.

                1. My mum pickled some garlic in vinegar, and they turned blue green. The odd thing is, she has done this before and they have been fine, so I don't know why these ones turned blue green.

                  1 Reply
                  1. re: moh

                    Vinegar can contain trace amounts of copper from being distilled in copper vessels. The acid copper combination together with a sulfur compound in fresh garlic turns it green. Copper pots or even other pans with trace amounts of copper can produce the same result while cooking.