Why do shrimp and crabs turn red when cooked?

Why do crabs turn red when cooked.

The pigment area of the exoskeleton of shrimp and crab contains a protoastaxanthin, which belongs to carotenoids, which is originally orange-red, but can be combined with different kinds of proteins, and will change to other colors such as red, orange, yellow, green, blue-violet, etc. When the protein is destroyed, denatured, or separated from the original astaxanthin, the color changes to the original orange-red, so the shell of the shrimp and crab will turn red after cooking. In the cortex under the shell of crabs and shrimps, there are many pigment cells, which can show different colors, and with the light and darkness of the environment, these pigment cells can also stretch or contract, when the environment is brighter, the pigment cells will stretch, the color of shrimp and crabs will be more distinct, and when the environment is darker, the pigment cells will contract, and the color of shrimp and crabs will not look obvious.

Under normal conditions, the shells of live crabs and shrimp are turquoise. However, when the crabs and shrimps are put into the pot, most of the pigments are decomposed when they encounter high temperatures, and only astaxanthin is not afraid of heat, and will not decompose when encountering high temperatures, but will show bright red, so the cooked crabs and shrimps will become red.

It's because of the shrimp. Crabs originally contained a substance called astaxanthin. will make the whole look green. When boiling. Because of the oxidation of astaxanthin. So turn red!

Among the carotenoids, the reduction of astaxanthin is the most important, which is the main substance that constitutes the red color of shrimp and salmon Prooriginal astaxanthin exists in the shell of shrimp, because it is combined with protein, so it becomes blue-purple, and once the protein is denatured by heat, it immediately returns to its original red color But when banao xanthin is combined with protein, it is still yellow. Tangerine. or red, which is why some shrimp or crabs are red in their shells when they are alive.

The color of the crab's body is mainly determined by the pigment cells in the carapace dermis. In the dermis of the crab carapace, there are various pigment cells, but most of them are blue-black, which is why live crabs are blue-black. Among these pigment cells, there is a pigment called astaxanthin, which is usually mixed with other pigments and cannot show its bright red color, but after boiling, other pigments are destroyed and decomposed, but it is not afraid of high temperatures, so the carapace of the crab shows the red color of astaxanthin.

However, in the dermis of the crab carapace, the distribution of astaxanthin is uneven. Therefore, you will find that after the crab is cooked, it is not red all over, and in places where astaxanthin is more distributed, such as the back part, it will appear extra red, while in places with less astaxanthin, such as the lower part of the crab legs, the red will be lighter. Since there is no astaxanthin in the abdomen of the crab, no matter how many times it is steamed, it will never turn red!

In addition to crabs, the discoloration of shrimp after cooking is also due to the above-mentioned reasons.

Because the shell of the shrimp contains astaxanthin and astaxanthin, the pigment is active when the shrimp is alive, so it shows blue-black. Astaxanthin is unstable and will be destroyed when it is heated, but astaxanthin is very stable, so it shows the red color of astaxanthin after cooking. This is also true for crabs that turn red after boiling.

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Analysis: Why do shrimp and crabs turn red when cooked? It's about chemistry.

It turns out that there is a bright red pigment in the shells of this cooked shrimp and crab. If the red shell of a crab is immersed in a chemical called acetone, the pigment will dye the acetone a beautiful orange red, and the shell will fade and lighten. Later, someone isolated this pigment from lobster eggs and called it astaxanthin.

Astaxanthin-containing animals are not only shrimp and crabs, but many crustaceans also use astaxanthin to dress themselves. Some small shells mainly contain fenocyanins, and some crabs contain pterenthin. These pigments, including astaxanthin, have a similar structure to carotene, and they are abundantly and widely distributed in nature.

The chemical name is ketone carotenoids, and they are the main components of the pigments contained in animals such as "shrimp soldiers and crabs".

The body color of living crustaceans varies depending on the species and the environment, but no matter what the body color of the living "shrimp soldier crab" is, as long as it is soaked or heated with formaldehyde, it will also turn red. This is because the pigment protein in the organism is denatured when it is heated, and the pigment that was originally bound to the protein "escapes" out, revealing the red color. In addition, after death, shrimp and crabs, due to the denaturation of proteins in the body, the pigment escapes, and the shell will also turn red.

1. The shrimp and crab turn red when cooked because the shrimp and crab contain astaxanthin.

2. The exoskeleton of shrimp and crab contains astaxanthin, which is a kind of carotenoid, after the pigment is combined with protein, it will turn into red, yellow, orange, green, blue-violet and other colors due to different proteins, when the protein is destroyed or denatured or the protein is separated from the pigment, the color will change back to the original orange-red, so after the shrimp and crab are cooked, the shell will turn red.