Why do crabs turn red when they die, and what are the characteristics of crabs when they die

Why do shrimp and crab 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.

Who said that when you die, you will turn red, only when you are ripe will you turn red, you lose your living cells, and your cell metabolism stops.

Eyes don't move: When a live hairy crab is touched, its eyes move automatically, while the eyes of a dead crab don't move on their own. Crab claws do not retract:

Pull the legs of the hairy crab apart with your hands, and the claws will not retract when pulled, indicating that the crab is dead. No bubbles: Put crabs in half a basin of water, and if they don't spit out bubbles for a long time, they are dead.

1. The eyes do not move: When the live hairy crab is touched, the eyes will automatically move, while the eyes of the dead crab will not move on their own.

2. The crab claw is not retracted: pull the leg of the hairy crab away by hand, and the crab claw will not retract when pulling, indicating that the crab is dead.

3. Don't spit bubbles: Put the crabs in half a basin of water, and if they don't spit out bubbles for a long time, it means that they are dead.

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 all kinds of pigment cells, but most of them are blue-black, which is also the reason why live crabs are cyan, in these pigment cells, there is a pigment called astaxanthin, usually it is mixed with other pigments, can not show the bright red color, but after the boiling section, other pigments are destroyed and decomposed, but it is not afraid of high temperature, so the carapace of the crab shows the red 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, in places where astaxanthin is more distributed, such as the dorsal part appears extraordinarily red, and in places with less astaxanthin, such as the lower part of the crab legs, the red will be lighter.

Since the abdomen of a crab does not have astaxanthin at all, it will never turn red no matter how many times it is steamed.

Summary. Hello dear no, it is possible that it is the color of the back of the crab normally. There are many colors on the back of crabs, including taupe, gray, pale red, and dark red, among others, and the color changes as the crab matures, so a reddish back may be a normal color.

But to determine whether the crab has deteriorated, you also need to observe carefully, such as whether the crab skin is off, whether the blood is black, whether the belly is soft, etc., if the above phenomenon occurs, it is likely that the crab has deteriorated.

Hello dear no, it is possible that it is the color of the back of the crab normally. There are many colors on the back of crabs, including taupe, jingheng gray, light red, and dark red, and the color changes as the crab matures, so a light red back may be a normal color. However, to determine whether the crab is spoiled, it is also necessary to observe carefully, such as whether the crab skin is peeled off, whether the blood is black, whether the belly membrane is soft, etc., if the above phenomenon appears in the lead liquid, it is very bright and exciting, it may be that the crab has deteriorated.

The hairy crab I bought, which was alive last night, died this morning.

The crab was originally brownish-black on the surface, and there was one crab this morning, pale red.

Motionless and falling, not moving.

Is it already spoiled?

It's probably spoiled. Hairy crabs should generally be eaten immediately after purchase, if the storage time code is too long, it is easy to make a spoiled hairy crab The color of the surface of the hairy crab will become pale red due to deterioration, and there will be no anti-sail balance when it falls again, showing that it is dead.

So dear, don't eat it, it's spoiled in this situation<>

Well, can you feed it to chickens.

It is not recommended to give crabs with spoiled feed to chickens, because crabs may contain pathogens that are harmful to poultry and livestock, which can be harmful to the health of chickens.

Ok thanks.

So don't give it to chickens either.

The dermis under the crab carapace contains four pigment cells: red, yellow, blue and cyan, and when the crab is heated to 100 degrees Celsius, the yellow, blue and cyan pigments will be decomposed and disappear, but the red pigment will not be destroyed, so that the cooked crab will show a bright orange color.

Crabs belong to the class molluscs, decapods, the body is protected by a hard shell, and breathe by gills, in terms of taxonomy, crabs and shrimp, lobsters, and hermit crabs are the same kind of animals.

There are about 4,700 species of crabs in the world, and about 800 species in China, and the main ones eaten are three-wart crabs, far-sea pike crabs, blue crabs and Chinese mitten crabs.

The red pigment contained in the dermis of shrimp is also called astaxanthin, which gathers more in the crab head, chest and feet, and rarely in the abdomen, so the phenomenon of crab cooked belly is usually white.

Because the color on the crab shell comes from a variety of pigments, including shrimp and crab white, the shrimp blue crab white interacts with the red astaxanthin to produce a blue-green color. When the crab is cooked, the white of the shrimp and crab is decomposed, leaving only astaxanthin, so it turns red. <

Because the color on the crab shell comes from a variety of pigments, including shrimp and crab white, the shrimp blue crab white interacts with the red astaxanthin to produce a blue-green color. When the crab is cooked, the white of the shrimp and crab is decomposed, leaving only astaxanthin, so it turns red.