Producer: Popular Science China
Production: X-Y Team (Dalian Institute of Chemical Physics, Chinese Academy of Sciences)
Producer: Computer Network Information Center, Chinese Academy of Sciences
It's crab season again, have you met the crab at the dinner table this year?
Under normal circumstances, the live crab is blue and black, a pair of steel and iron bones, after steaming, it will change into a big change, the crab shell becomes red, and the bright color is more mouth-watering.
Having eaten so many crabs, do you know why the shells turn red during the steaming process?
Who was the first person to eat crab?
Crabs, a genus of soft-carapaceous, are crustaceans that are protected by hard shells.
Chinese have eaten crabs since ancient times, and the ancient literati regarded crab eating as a pleasure, and they relished crab tasting. Shi xian Li Bai has a special love for crabs, especially likes to eat crabs with wine, once said that "crab claws are gold liquid, bad hills are Penglai, and must drink fine wine, take the moon drunk on the high platform." A generation of people Su Dongpo also became addicted to crabs, often exchanging poems for crabs, "can laugh at Wu Zhongfeng too defensive, a poem in exchange for two sharp groups."
Before and after Chongyang, it is the season when the chrysanthemum crab is fat, about three or two friends, enjoy the chrysanthemum crab together, is not beautiful and fast!
However, the appearance of the crab does not meet the traditional gastronomic standards, who was the first person to have the courage to eat crab?
Image credit: Veer Gallery
Legend has it that thousands of years ago, there was a pair of eight-legged and viciously shaped beetles in the lake, which not only dug holes to destroy rice fields, but also used chelating to injure people, so it was called "clipping worms". This is also the original name of the crab.
Later, Dayu Zhishui came to this place and sent Zhuang Ding Ba Xie as an overseer. The presence of insects led to slow progress in the project, and the PLO came up with a clever plan to let everyone dig a ditch on the edge of the city and fill the ditch with boiling water.
The trapped insects that climbed here fell into the ditch and burned to death, and their bodies were red and emitted a seductive umami smell. The PRC broke open the carapace, and the fragrance was actually stronger, so it had the courage to take a bite, who knew that the taste was delicious. Since then, the fearsome pest has become a household name, praised by generations of gourmets.
Later, people were grateful for the PLO's wisdom to solve the problem of people and insects, and they dared to do the work of the world, so they overthrew the word "solution" in the name of the PLO above the word worm, calling the worm "crab".
Astaxanthin: The secret of crab shell discoloration
So, why does the crab shell change from green to red during the cooking process?
Originally, there was a dermis layer under the shell of the crab, which was scattered with many pigment cells, of which the orange-red astaxanthin was the most. The mystery of the discoloration of the crab shell is in it.
The astaxanthin in live crabs binds to different kinds of proteins to appear blue-violet or cyan-black, called astaxanthin. Once in a high temperature environment, such as a pot of about 100 ° C, the protein will be denatured by heat, and the binding force between astaxanthin and astaxanthin will gradually weaken. Slowly, protein-binding astaxanthin changes back to astaxanthin that does not bind protein.
At the same time, other types of pigment cells in the dermis layer are slowly decomposed because they are afraid of heat, and only astaxanthin is not afraid of heat and is retained.
In addition, because astaxanthin is mostly concentrated in the head, chest and feet, and the abdomen is very rare, so "crab cooked belly white" is also a common phenomenon for us.
Common live crab on the left, cooked crab after cooking on the right (Image: Veer Gallery)
Astaxanthin is not only found in aquatic crustaceans such as shrimp and crabs, but also in the feathers of some fish and birds.
The role of astaxanthin is not just as simple as color development, it is also the strongest antioxidant in nature discovered by humans so far, known as "super vitamin E" and "super antioxidant".
Some astaxanthin-rich foods (Image: Veer Gallery)
Three tricks to pick a crab worth entering
As the saying goes, "September full navel October tip", refers to the lunar calendar in September to eat female crabs, crab navel is round, then the female crab yellow full of flesh thick; lunar October to eat male crabs, crab navel is pointed, at this time male crab cream foot meat firm.
And how to choose a fresh and fat crab is really a technical job. In simple terms, it can be summarized as "one pinch, two teases and three looks" three skills.
"One pinch": that is, pinch the crab's claws with your fingers to check the meat quality of the crab. Crabs with fully mature molting shells are generally hard and strong, while unripe crab claws are softer.
"Two teases": that is, teasing the eyes of crabs with their hands. If it reacts immediately, it indicates vitality; if the eye is prominent and unresponsive, it may have died. Turning the crab upside down, with its abdomen facing the sky, can quickly turn and crawl, indicating that the crab has vitality; not being able to turn it over or turning it over hard indicates poor vitality.
"Three looks": that is, to see the shape of the crab. The back of the shell is dark green with a gloss, indicating that the flesh is thick and strong; the tail end of the crab's umbilicus protrudes and reveals red, which is generally full of cream and fat.
Crabs being sold in the market (Image: Veer Gallery)
The most common way to eat crab is steaming. After boiling water in a steamer, put the crab in, steam on high heat for 5 minutes, then reduce heat to continue steaming for a period of time. The steaming time depends on the size of the crab, generally 150g crab should continue to steam for about 10 minutes; for every 50g increase in body weight, the duration increases by 2 minutes.
In addition, you can also see the color of the crab shell with the naked eye, most crabs will appear orange-red when cooked thoroughly, if the crab shell color is blue, you need to cook for a while.
Autumn wind, crab feet fat, the next time you meet with the "crab" old friend, you can show off that we already know the secret of its discoloration.
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