Friends who have bought seafood know that after fresh seafood is slaughtered, even if it is just taken home and stored in the refrigerator for a short period of time, after cooking, the taste is not as fresh and sweet as live seafood, and the meat is not as "chewy" as when fresh. This is quite different from pork, beef, and mutton. On the contrary, pork, beef, and mutton need to be slaughtered and left to mature for a while before the meat becomes fresher and more tender. Why on earth is this? Why doesn't fresh seafood taste good when it dies? To understand why seafood doesn't taste good when it dies, one must first understand the general changes that occur after the seafood dies. Seafood is rich in protein and unsaturated fatty acids, and due to living in water, various parts of the body often carry a lot of bacteria and other microorganisms. It can be imagined that after the death of seafood, bacteria and other microorganisms lose the restraint of the seafood immune system and will rapidly multiply on this "paradise" filled with proteins and fatty acids, causing the seafood to spoil and deteriorate. Soon, the enzymes in the seafood body will begin to break down proteins, causing the originally tight muscle tissue to be destroyed, becoming loose and soft, and the taste to deteriorate; Rich unsaturated fatty acids are oxidized, producing various odorous substances such as aldehydes, ketones, and other volatile substances such as isopropylbenzene, styrene, ethyl acetate, etc; Myoglobin is oxidized to high-speed iron myoglobin, causing the originally pink red seafood to turn gray and brown; The rapid proliferation of bacteria can also cause black and gray spots on the surface of seafood; Therefore, once seafood dies, the meat quality, aroma, and color will quickly change, and the color, aroma, and taste will all decrease, naturally making it unappetizing. At this point, it's actually okay, it's just not delicious. Some seafood can release harmful toxins to the human body after death, which is even more dangerous. For example, tuna, mackerel and sardine are rich in histidine. If they are not preserved properly after death, it is very easy for bacteria to convert histidine into histamine under high temperature. Histamine can cause food poisoning, leading to serious conditions such as rash, headache, vomiting, diarrhea, difficulty breathing, and coma. Therefore, if you want to eat seafood safely, you must be cautious in choosing seafood varieties and avoid those that are prone to toxicity or toxin production. Is the freshness of seafood a double-edged sword? Fresh seafood doesn't even need any seasoning, just boiled in plain water, it's incredibly fresh and sweet, and the fresher the seafood, the more pronounced this fresh sweetness becomes. The strong freshness of seafood mainly comes from the abundant "umami amino acids" in the body. The term 'umami amino acids' refers to a type of amino acid with a unique umami taste, such as glutamic acid, aspartic acid, phenylalanine, glycine, tyrosine, etc. The sodium salt of glutamic acid, monosodium glutamate, is the main component of monosodium glutamate. The content of glutamic acid and aspartic acid in seafood is generally high. At the same time, seafood also contains a large amount of nucleotides, such as adenosine monophosphate, inosine, and guanosine, which can amplify the taste of umami amino acids such as glutamic acid and aspartic acid, making the freshness of seafood even higher. In addition, fresh seafood also has a slight sweetness, mainly from glycogen in the meat and some slightly sweet amino acids such as glycine and alanine. Studies have shown that seawater shrimp and crabs contain higher levels of glutamic acid, disodium inosine monophosphate, and adenine nucleotides than freshwater shrimp and crabs. This is probably one of the reasons why people think seafood tastes better than river seafood. But these umami substances seem to be a double-edged sword. When seafood is alive, the above-mentioned umami substances are constantly produced and accumulated, making the seafood "fragrant to the point of confusion"; Once seafood dies, it begins to rapidly decompose, greatly reducing its edibility: the amino acids that decompose into a savory flavor release a pungent ammonia smell, which is unpleasant. Some sulfur-containing amino acids can also produce hydrogen sulfide after decomposition, emitting a foul egg odor; Glycogen, which used to bring sweetness to meat, also accelerates its breakdown, releasing lactic acid and giving seafood a rancid sour taste; There is also a substance present in seafood called trimethylamine oxide, which can bring a fresh and sweet taste to seafood. However, after the seafood dies, it quickly decomposes and produces trimethylamine and dimethylamine, which can give the seafood a strong fishy smell. The combination of the above-mentioned odors, sourness, and fishy smell can make dead seafood turn pale and cause people to shy away. How to choose and store fresh seafood if you want to eat it? The most convenient way to enjoy fresh seafood is to directly board a fishing boat and catch while eating; The second best way is to wait at the shore and buy seafood that has just been salvaged by fishing boats. But if we don't live in coastal areas, these methods are not convenient for modern people, and we can only go to markets or supermarkets to purchase. So you will definitely need the following tips: 1. Choose live seafood. It should be noted that in live seafood, it is also important to observe their movements and reaction speed. You can gently touch it with a fish pick, whether it's fish, shrimp, crab or shellfish. Those who move faster and respond quickly to external stimuli often have higher freshness. 2、 Look at the meat quality. The meat is firm and elastic, and the tentacles are not sticky, indicating that the protein has not been broken down and the freshness of seafood is higher. 3、 Weigh it. After seafood dies, nutrients such as protein are broken down, which can cause the weight of seafood to decrease. Therefore, it is recommended to choose seafood of the same size that is more "pressing" and often fresher. 4、 Try not to buy too much, it's best to buy and eat now. If you can't finish all the seafood you buy at once, you can also divide it into small portions and store them in the freezer compartment of the refrigerator. This way, taking one portion each time for thawing can avoid the impact of repeated thawing and freezing on the meat quality. By the way, last but not least, there is a way to save money: frozen seafood has almost no loss of nutrition compared to fresh seafood, and its freshness is also maintained relatively well. The disadvantage is that seafood has a high water content, which makes it easier to produce ice crystals during the freezing process, affecting the elasticity of the meat. However, considering that frozen seafood is convenient to store and much cheaper than fresh seafood, it is still worth recommending. For some seafood that does not have a significant impact on taste after freezing, such as prawns, frozen options can be chosen. During the Mid Autumn Festival, bring this selection guide to the supermarket to choose seafood for your home, be prepared. (New Society)