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I'v been given some prawns from parents where they bought in bulk. The prawns leak a blue dye? Does anyone know if this is normal?

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I've seen that. I think it's actually natural. As a matter of fact, I just threw away a few shrimp that had reached their freezer burn limit. They were quite blue as was the absorbent sponge in the package with them. –  Jolenealaska Jun 27 at 6:36
    
Thanks. I was worried maybe there was some sort of chemicals been added to the prawn. –  user172839 Jun 27 at 6:41
    
I can't say with authority that there are no artificial colors involved, but I don't think so. I have no doubt that one of our experts on the subject will provide an answer before long. –  Jolenealaska Jun 27 at 6:47
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up vote 7 down vote accepted

The color should not be a problem for you as long as red coloring in beef packaging doesn't bother you.

That's right, that blue dye is blood. Crustaceans, like the prawn, crab, and lobster, and horseshoe crabs have hemocyanin in their blood to transport oxygen instead of hemoglobin, which we have. Hemocyanin has copper in it to give it its color rather than the iron hemoglobin has.

So to answer your question specifically: Yes, it is normal.

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Believe it or not, the opposite is actually true... if you buy cooked shrimp in some markets, they've been dyed pink to appear more attractive. –  logophobe Jun 27 at 14:36
    
Do you mean they are dyed pink because their blood is normally blue and weird to most people? What is opposite? –  Dispensador Jun 27 at 15:03
    
You're entirely correct about raw shrimp/prawns. That coppery-blue color is completely normal. I simply mean that what some consumers consider the "natural" color of shrimp (i.e. pink) is sometimes exaggerated by retailers. If I disagreed with you, I'd offer my own answer instead :) –  logophobe Jun 27 at 15:20
    
Thanks for that. I have marked this as the accepted answer –  user172839 Jun 30 at 0:17
    
Isn't the red juice in beef myoglobin not blood? Animals are pretty much completely drained of blood in slaughtering –  David Hayes Jul 2 at 18:39
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