Yes, a special species of purple crab is a treasure in Tianjin aquatic products. The purple crab, the size of a copper coin, lives in a mud nest by the river every winter and must be caught by breaking the ice. Although the crab body is small, the crab yellow is full and fat. When it is raw, it is pig liver color, and when it is cooked, it will turn orange-red. It is so delicious that people are salivating. Tianjin purple crab is a kind of Chinese mitten crab. It's very small, only the size of a coat button. Uncover the crab cover, the crab yellow is purple in pig liver, and it turns orange after cooking, which is very delicious. Purple crabs are all produced in cold winter, so they are often used in assorted hot pot. Every winter, people gather in mud pits on the banks of the river and have to break the ice to catch them. Although small, its abdomen is white and muddy, and it tastes delicious. Because its crab yellow is extremely rich, it shows a layer of purple through the thin crab cover, hence the name. It was a tribute in the Ming and Qing Dynasties. This dish is one of the traditional dishes in northern China. Similar to "instant-boiled mutton", you can eat it while rinsing. But its ingredients and taste are better than instant-boiled mutton. Whenever it's the season when thousands of miles are frozen and the snow is falling in Wan Li, three or five confidants and a pot of fine wine will enjoy themselves, with endless flavor and fun. It is characterized by fresh and tender ingredients, delicious soup and little loss of nutrients, which is quite nourishing. Extended data:

Nutrients per100g crab edible part contains protein17.5g, fat 2.8g, phosphorus182mg, calcium126mg, iron 2.8mg and abundant vitamin A and vitamin B 1. The composition of Scylla serrata is rich in protein, among which the content of female gonad is as high as 30.98%, ranking first in fresh protein. Protein of Scylla serrata has a complete range of amino acids, and the score of essential amino acids is 84.23 ~ 93.58. Scylla serrata is rich in fat and unsaturated fatty acids (UFA). The unsaturated fatty acids in muscle are 74.58%, EPA is as high as 18.04%, and DHA is 13.52%. The content of unsaturated fat in Scylla serrata is very high, especially omega-3 fatty acids, EPA and DHA, which cannot be synthesized by human body. EPA can obviously reduce the values of triglyceride (TG) and cholesterol (TC) in serum, prevent platelet aggregation, delay thrombosis, prevent cardiovascular and cerebrovascular diseases and prostatic hyperplasia, and DHA can promote brain development, enhance brain learning and memory ability, and prevent brain aging. Scylla serrata is a kind of food with high potassium and low sodium, and Scylla serrata is more beneficial to hypertensive patients. The content of Ca in its liver is extremely high, second only to stone snail, shad, dried shrimp, dried shrimp skin and clove fish, and natural organic calcium is easily digested and absorbed by human body. The content of magnesium, iron, copper, zinc, manganese and other essential elements in Scylla serrata is also high. The selenium content of various components of the blue crab is very high, especially the female gonad.