raw fish with metallic glisten

I ordered sushi this evening from a reputable NYC sushi restaurant, where I generally find the fish to be quite good. I'm particular when it comes to fish, especially raw fish. When the sushi was delivered, over an hour later, I unwrapped it to find that the salmon, in my smoked salmon avocado roll, had a metallic, bluish glisten to it. I've seen this once before, but only after I left raw fish in the fridge one day too long. I was surprised to see this on smoked fish. Any ideas what the cause of this may be? I'm assuming it's indicative of something not very good.

  • Posted by: ATG117
  • June 15, 2011


thirschfeld June 17, 2011
bacon does this too. Birefrengence happens more often with cured proteins. Smoked salmon I am guessing means lox, cured and cold smoked, because regular salmon rarely has this effect but tuna almost always does.
ATG117 June 17, 2011
Also, the other time I've seen this, it was indeed with raw sushi grade tuna.
ATG117 June 17, 2011
Hardlikearmour, I think you may have hit the nail on the head. It does look like a rainbow. I was having a hard time trying to describe the effect. "Rainbow glisten" would probably have been more accurate. Quite interesting. Thanks!
boulangere June 16, 2011
Fascinating, HLA. I've seen this, too, and ate the fish anyway and lived to tell the tale. Surely You're Joking, Mr. Feynman is one of my favorite books, Panfusine.
SKK June 16, 2011
Between HLA and Panfusine, I am getting an unexpected education in science! Love this foodpickle.
Panfusine June 16, 2011
Birefringence... LOL HLA: your defining style of the word & description of the phenomenon just reminded me of a similar anecdote from Richard Feynman's book 'surely you're joking Mr Feynman'.. about the word 'Triboluminescence' (light emitted when sugar crystal are crushed)
nutcakes June 16, 2011
Another possibility is if it was prepared with garlic, sometimes garlic can turn blue, so it might make the fish blue. I looked this up several times and found it is safe to eat. But I like hardlike armours answer better so plus one.
hardlikearmour June 16, 2011
It could just be birefringence. This is part of a transcript of a Good Eats episode about tuna. I don't see why the same couldn't apply to salmon.

"Speaking of color, you ever notice the rainbow effect that sometimes appears on the surface of freshly cut tuna? It's not from age and it's not fat. It's birefringence.
[reading from a book] "*Anisotropism of the refractive index which varies as a function of polarization and fre ... " [gives up]
Here's the deal. This surface is pretty smooth. But, if you look closely, you'll see it's actually a vast landscape of parallel fibers. When cut, the reduced surface pressure coaxes microscopic beads of moisture to the surface, each one of which acts as an independent prism. When viewed in concert, they look like a rainbow."
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