Why lobsters and crabs turn red on cooking

These two Sea foods are mouthwatering and popular all over the world. So much so that fairs are held to celebrate the lobster.  One such festival is held in Rockland, Maine which is attended by thousands.

lobster

When cooked these creatures turn coppery red. Although it is not necessary to become a chemist to become chefs but cooking is a science where chemistry takes place at each step. Some chemicals break down to get converted into edible and easily digestible. Similarly in many foods there are color changes when cooked which is also due to chemical modification of ingredients. Here also, chemistry is occurring.

Normal lobster is of muddy color when alive. But the final color is dependent on the amounts of a pigment called astaxanthin which is also the pigment responsible for the red color of carrots, pink of flamingos, salmon and crabs. This pigment is red in color when free. It’s chemical structure is given below.



due to the ketone and alcohol groups this compound is very active chemically easily binds other chemicals like proteins. pigment is a. powerful antioxidant. Lobsters ingest it keep stress of survival under control has been found be beneficial human beings.

What happens in the lobster is that this pigment binds to the proteins in its skin. Due to this binding, it is forced to change its geometric structure and gets twisted to fit in. Depending on the type of protein it bonds to, there’s either what’s called a bathochromic shift, which turns the pigment blue, or a hyspochromic shift, to yellow. When you’re looking at a lobster, you’re seeing light reflecting through different layers of free and bonded astaxanthin–a lot of colors mixed together, hence the muddy brown.

So the final color is a combination of many colors like red, blue and amount and type  of proteins present in the body of lobster and the age . The muddy color is good for camouflaging from the predator because it becomes indistinguishable from the muddy water.

When the lobster is cooked the proteins are denatured and release the astaxanthin pigment turning the cooked meat into coppery red.

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