As an unmuddied lake, Fred. As clear as an azure sky of deepest summer.

July 14, 2007 2:08 AM

Why did my garlic turn blue?

I was cooking salmon on the barbecue yesterday and when it was done I noticed the garlic had turned bright blue. I looked it up and it seems that garlic in pickling solutions will sometimes turn blue. There are various explanations of this, but the most common one is that in an acidic solution, sulfur containing compounds in the garlic react with even minute amounts of copper to form copper sulfate. This is what I had assumed had happened, because I remembered hydrated copper sulfate being exactly the same colour.

There were a few other explanations of how the colour forms, but assuming that this explanation is correct, where did the copper come from? The other ingredients were soy sauce, rice vinegar, ginger, and slices of apple on a wild sockeye fillet. I cooked it in tinfoil.

I apologize in advance for what is probably a trivial question. It's just been bothering me for a whole day now.

posted by [expletive deleted] to Food & Drink (7 answers total)

Farmed fish are fed copper, and shellfish blood uses copper in place of iron, but wild fish shouldn't have too much. Are you sure it isn't some other kind of reaction related to PH or smoke. What kind of fuel, coal, gas, wood chips?
posted by BrotherCaine at 2:37 AM on July 14, 2007

This page says that acidity can turn the garlic blue if it's young or not properly dried. I had a feeling that if garlic had grown in copper-rich soil that could also be a factor; but I could be making stuff up.
posted by ambilevous at 2:57 AM on July 14, 2007

Response by poster: Salmon is red because of pigment from the krill that they and their prey species eat, and sockeye is the deepest red of all salmon. This could explain why wild sockeye would contain some copper.
posted by [expletive deleted] at 3:40 AM on July 14, 2007

Also, to BrotherCaine's point, the fact that it was labeled "wild" in the store doesn't necessarily mean it wasn't farmed.
posted by LairBob at 3:43 AM on July 14, 2007

Best answer: Fresh garlic + acid (in your case, vinegar) = blue garlic. When I catered, we made a marinated vegetable salad in the spring with fresh garlic from the farmer's market specifically because the garlic would turn blue, and it always made for interesting conversation at the buffet table. There's nothing wrong with it - it's just, you know, blue.
posted by TryTheTilapia at 8:41 AM on July 14, 2007

Response by poster: LairBob, I've lived my entire life on the west coast, and until I was about 13, my father was a commercial salmon fisherman (troll and gill net). Believe me, I can tell the difference between farmed and wild. One dead giveaway that most people don't know about is texture. Wild salmon is firm, but farmed salmon will have a distinctly mushy texture. Also, farmed salmon may be fed the same pigment that turns wild ones red, but sockeye hang on to the pigment better, and they have a complicated life cycle that has thus far made them impossible to farm--they spend a year in fresh water, typically lakes, before heading out to sea.

As for the article you posted, it doesn't surprise me. Personally, I only really buy sockeye, so avoiding farmed fish is pretty simple. I've seen farmed Atlantic salmon being sold as wild sockeye in Vancouver, and the difference is pretty stark. As for where all the wild fish goes: typically Japan. Fish buyers from Japan would literally come to public wharves with duffel bags filled with cash, and buy every fish from every boat. It was a pretty funny sight.

Thanks Tilapia. Your anecdote, along with others I've found, has lead me to believe that the copper is in the garlic itself. This makes sense since the colour is evenly distributed, and not concentrated on the surface.
posted by [expletive deleted] at 10:31 AM on July 14, 2007

Sorry--no offense intended. Was just pointing out that if the answer depended on a distinction between "wild" and "farmed", then for most folks--at least those of us who weren't raised by salmon fishermen ;) --the line isn't always easy to draw.
posted by LairBob at 1:03 PM on July 15, 2007