Yesterday morning I put some raw prawns (shell removed) into vinegar (more specific this one), and put them in fridge. When I came back at night all of them turned red, which looks cooked, except those not covered by vinegar.

Why do the raw prawns change colour?

  • 1
    $\begingroup$ Heat and Acids denature proteins. $\endgroup$
    – AMR
    Jan 16, 2016 at 17:34
  • $\begingroup$ To me, this should be more suitable for Chemisty-SE. $\endgroup$ Jan 16, 2016 at 21:47
  • $\begingroup$ The way I understood lobsters was that their shells have molecules of many different colors, giving them a mottled green-brown appearance. When cooked, the non-red molecules are destroyed, leaving only the red color. Vinegar may do something similar to the non-red molecules by being acidic, maybe the pigments are like pH indicators. I know shrimp aren't lobsters, but are probably close enough. $\endgroup$
    – user137
    Jan 17, 2016 at 7:20

1 Answer 1


The prawn has proteins (meat, muscles).

Beef is red because the muscle proteins in it have a molecule that binds oxygen called myoglobin (whereas our red blood cells have hemoglobin that allows them to carry oxygen better).

In fish you know the meat is white because there is no myoglobin present (in the muscle proteins), but another molecule that still binds oxygen but doesn't look red.

When you add heat or acids (vinegar) to the meat, the proteins get denatured, change their shape and their colour too. You get red shrimps by heating the proteins in them.

Hope this helps

  • $\begingroup$ @Him , please let me know if you understood my answer and if you found it helpful please mark the question as checked $\endgroup$
    – Vladimir
    Jan 17, 2016 at 22:16

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