Many people like to eat shrimp, but few people know what effect the shrimp has, and the shrimp head will turn black during the preservation process. Is it not fresh that the shrimp head turns black? 　　 Is it not fresh that the shrimp head turns black? To understand why shrimp heads turn black, you need to recognize a substance-tyrosinase, which is commonly found in animals and plants. Although the structure of tyrosinase in different organisms is very different, the basic function is similar. Under the action of tyrosinase, tyrosine can gradually form quinone substances, and then form black substances such as eumelanin and pheomelanin. Tyrosinase is distributed throughout the shrimp, but the tyrosinase activity in the head is the strongest, and the enzyme activity in the abdomen and tail is lower. Therefore, the shrimp head always turns black first, then the belly and tail. 　　 The blackening of shrimp is mainly due to the action of enzymes, which has little to do with microorganisms. Even under freezing or cold storage conditions, tyrosinase is still active, so blackening still occurs. The head of the shrimp is also where the viscera of the shrimp is. If the shrimp happens to eat a lot of dark algae, such as brown algae, before fishing, the shrimp may also have black hair. In addition, the undigested feed of farmed prawns may also appear black. Therefore, a black shrimp head does not necessarily mean that the shrimp is not fresh. From this point of view, the blackening of shrimp heads is not so scary, and it needs to be treated correctly. 　　How to judge the freshness of shrimp 　　1. The surface of fresh shrimp is dry 　　The surface of the fresh shrimp is clean, and it feels dry to the touch. But when the shrimp's body is about to deteriorate, the mucus-secreting granular cells under the carapace disintegrate, and a large amount of mucus seeps into the body surface, making it feel slippery to the touch. If the shrimp shell is sticky, it means the shrimp has gone bad. 　　2, fresh shrimps are bright in color 　　 There are different types of shrimps, and their colors are slightly different. Fresh prawns, roche prawns, and grass prawns are blue, sea-caught prawns are pink, and bamboo prawns and giwei prawns have black and white patterns and slightly pink. If the shrimp has black hair, it means that the shrimp is not fresh. The whole shrimp is darker and not bright, which means it has deteriorated. 　　3, fresh shrimps are curved 　　 The head and tail of fresh shrimp are intact, and the head and tail are closely connected to the body. The body of the shrimp is relatively strong, with a certain degree of flexibility and curvature. In the stale shrimp, the head and body, shell and meat are loosely connected, and the head and tail are easy to fall off or separate, and cannot maintain their original curvature. 　　4, fresh shrimp shells must be hard 　　 Fresh shrimps have hard shells, bright cyan color, sharp eyes, firm flesh and very strong smell. If the shell is soft, the color is gray, the eyes are sunken, and the shell flesh is slightly separated, it means that the shrimp has just died.

Seafood food contains a lot of protein and nutrients, and is an important source of a healthy diet. Eating some seafood every day can ensure a balanced diet, which is very beneficial to heart health and the growth of children. However, improper consumption of seafood can easily cause "food poisoning", so you need to be extra careful when buying, handling and storing seafood. Pay attention to the purchase of fish and shrimp: 1. Buy fresh fish and shrimps that are frozen or placed on a bed of unmelted ice (preferably covered by a cover) 2. Choose fish that smells fresh and does not smell fishy or ammonia. 3. Fresh fish eyes should be clear and slightly prominent. 4. Whether it is a whole fish or a fillet, the meat should be firm and elastic, with bright red gills and no white mucus. 5. There is no lightening, darkening or cracking around the fillet. 6. Shrimp meat should be translucent and shiny, without peculiar smell. 7. Some frozen fish and shrimp packaging will indicate the freezing time and temperature, you can check it when you buy it, and choose the right seafood. Pay attention to the purchase of shellfish seafood: 1. If the shells of oysters, clams, mussels and other shellfish have cracked, do not buy them. 2. Lightly touch and tap the shell of the shellfish seafood with your hand to buy the shellfish that will automatically close. 3. Dead lobsters and crabs have poor meat quality. Therefore, when purchasing, observe whether the legs of the shrimps and crabs move to determine whether they are fresh. Frozen seafood is easy to thaw on the way to transport or take home after purchase, it is best to control the time it is placed in warm temperatures. 1. Do not buy frozen seafood with damaged packaging. 2. Do not buy frozen seafood with frost or ice crystals on the packaging, because such seafood may have been frozen for a long time, or it may be frozen again after thawing.

The most common problem encountered in cooking seafood is that the head is overcooked and the bite is too old and tough. The sweet juice of itself has also been lost, and the taste is the same as chewing wax. Today, I will use squid as an example to teach you how to cook delicious food in one simple step! Ingredients: some fresh squid practice: 1. Pour the water into the pot to a position where the squid can be submerged, boil the water and put in an appropriate amount of salt (the squid has not yet been put in the pot). *Do not rinse the squid in tap water as it will lose its sweetness. 2. After boiling, turn off the fire, soak the squid in salt water for two minutes and then pick it up. Tips: Why soak in salt water? The squid soaking in salt water is to maintain the sweetness and improve the crispness. It is normal for the water in the pot to appear dark red when picked up, because the squid will release water during the soaking process. The blanched squid should be almost fully cooked, but not too old or too tough, and still maintain a fresh taste, whether it is to be eaten directly or the blanched squid is processed into other dishes (such as three cups) Squid). The blanched squid will no longer be watery, it will not dilute the taste of the dishes, or affect the thickness of the sauce!