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Steamed clams - juice turned a strange blue-ish color

I just picked up some fresh littlenecks from the farmers market yesterday (they are from Long Island). I steamed the clams in some wine in a stainless steel saute pan, and removed the clams as they opened. After all the clams were opened, I let the juice reduce down a bit for a few minutes. The strange thing is that the juice turned a weird, blue-ish type color. The juice tastes great and the clams are fresh, but the color is unappetizing. Anyone know why this would be? And can I still eat the clams?

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  1. You better wait til someone more intelligent than I am chimes in, but my first guess is it's the sulfites in the wine that are turning the juice blue.

    1. Did you have garlic in there? I've had a blue coloring issue with raw garlic and wine in the past.

      4 Replies
      1. re: Terrie H.

        Usually the garlic itself will turn blue. I've had that happen. Never the liquid, though.

        1. re: C. Hamster

          Very true, though I thought it might leach into the liquid, depending on what was going on.

          1. re: C. Hamster

            Yes to both, and I think it's b/c of the sulfur in the garlic. This may be an old wives' tale....but I'm wondering if there was sulfur/sulfites sufficient to turn it blue in the wine? I don't know enough about wine chemicals to say. And yes, maybe the garlic leached too.


            1. re: pinehurst

              The only thing is that winegod didn't say there was garlic in his pot, and I was asking if there was, just as a theory. Guess more info and then input from our chemically-knowledgeable cooks is needed.

              Completely OT, but I'm picturing a scene from Bridget Jones' Diary where she attempts to cook something wrapped in blue string and turns her whole dish an eerie blue color. ;o))

        2. There was nothing in the pan besides wine and the clams.

          1. Winegod...
            I don't know if this post might help. I'm sleuthing with you!


            1 Reply
            1. re: pinehurst

              Pinehurst - this seems like the closest to an answer that I've seen (in the link Jruckel explains that the blue color comes from a chemical change when scallops are spawning, so I assume there could be a similar process with clams - they are both bivalves, after all). A google search returned nothing in terms of any clues. I hate wasting food and feel bad throwing them out, but the clams just look so unappetizing sitting in this weird, blue liquor. I will have to ask the fish monger at the Farmers Market why this happened. By the way, I have bought a variety of fish and shellfish from this purveyor, and the product has always been of the utmost quality.

            2. 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 Replies
              1. re: maria lorraine

                I thought there was no garlic in the pot, only clams and wine.

                1. re: alkapal

                  Oops. My bad. No garlic, Winegod?

                  Then my second guess has to do with the pigment cells in a clam's shell, and that the pigment is alcohol-soluble. I think the pigment cells are called iridophores.

              2. Another Chowhound thread on this:
                Anyone ever had garlic turn blue-green while cooking?

                Here's the explanation from food scientist Harold McGee in a New York Times article called "When Science Sniffs Around the Kitchen":

                "I hear every year from cooks who have been alarmed at seeing normally pale garlic turn bright green and even blue, sometimes when the cloves are pickled whole, sometimes when they’re chopped and cooked with other ingredients."

                The blue color comes from "the same handful of sulfur compounds and enzymes that give the allium family its unique pungent flavors. They are perfectly safe to eat."

                The part on garlic turning blue is just over halfway down in the NYT article:

                1. The garlic turns blue. Very odd looking.

                  But I have never had the blue/green color leach into the broth

                  1. I think the clue is in reducing the broth. The OP mentioned that things were fine in the beginning, and she/he removed the clams as they opened. The blue color appeared as the wine reduced. What is not mentioned is the type of wine (presumably white, but nothing as to age, quality, etc.). The people who mentioned sulfites may be on to something. As the wine reduces, the concentration of the sulfites increases. No change in the amount, but concentration increases as the solvents (water and alcohol) are removed. At some point, they, and possibly other chemical constituents of the wine, were concentrated enough to react with the proteins in the broth (which may have included algae ingested by the clams...another factor. Also, cyanobacteria _"blue-green algae"- live in the same sediments as the clams.).
                    Also, isn't there a Swiss recipe for "blue" trout, in which the poaching vinegar turns blue?

                    1 Reply
                    1. re: EricMM

                      Interesting. The wine was some leftover white Rioja which had been in the fridge for a few days. Yes, the color seemed fine until I reduced the clam juice/wine broth for a couple of minutes.