Shrimp is one of the most popular seafood ingredients, but when we buy or eat shrimp, we often see that the shrimp heads are black. Why is this? Can shrimp with black heads still be eaten? Let's see what the experts have to say.
Why do shrimp heads turn black?
On this issue, Dr. Zhong Kai, a food safety expert, explains: To understand why shrimp heads turn black, you first need to know about a substance called tyrosinase. It is widely found in animals and plants. Although the structure of tyrosinase varies greatly among different organisms, its basic function is similar. Under the action of tyrosinase, tyrosine can gradually form quinones, which then form black substances such as eumelanin and pheomelanin. Tyrosinase is distributed throughout the shrimp's body, but the activity in the head is the strongest, while the activity in the abdomen and tail is lower. Therefore, the shrimp head is always the first to turn black, followed by the abdomen and tail.
The blackening of shrimp is mainly due to the action of enzymes and has little to do with microorganisms. Even under frozen or refrigerated conditions, tyrosinase remains active, so blackening can still occur. The shrimp head is also where the internal organs are located. If the shrimp happened to eat a lot of dark-colored algae, such as brown algae, before being caught, its head may also turn black. In addition, undigested feed from farmed shrimp can also appear black. Therefore, a black shrimp head does not necessarily mean the shrimp is not fresh.
From this, it seems that a black shrimp head is not such a scary thing; it needs to be understood and handled correctly.
Next, let's share how to choose fresh shrimp.
5 tips for choosing fresh shrimp
1. Curved body shape. Currently, many people don't like to eat shrimp with a curved body, mainly because such shrimp generally look smaller and are difficult to peel. But what they don't know is that fresh shrimp should have a complete head and tail, which are tightly connected to the body. The shrimp body should be firm, with some elasticity and curvature. If the shrimp head and body, or the shell and meat, are loosely connected, the head and tail are easy to fall off or separate, and cannot maintain their original curvature, then it is very likely that the shrimp is not fresh, and it might even be a dead shrimp.
2. Dry surface. Live shrimp have a clean and dry exterior to the touch. However, when the shrimp is about to spoil, the granular cells that secrete mucus under the shell break down, causing a large amount of mucus to seep onto the surface, making it feel slimy. If the shrimp shell is sticky, it means the shrimp has spoiled.
3. Bright color. Different types of shrimp have slightly different colors. Fresh Chinese shrimp, giant river prawns, and grass shrimp are bluish-green, wild-caught prawns are pink, and bamboo prawns and grass prawns have black and white patterns with a hint of pink. If the shrimp head is black, it is not fresh. If the entire shrimp is dark and dull, it also indicates that it has spoiled.
4. Shell and meat tightly connected. In fresh shrimp, the shell and meat are stuck together tightly. When peeling the shrimp meat by hand, the meat is sticky and requires some effort to remove the shell. The intestinal tissue of a fresh shrimp is also tightly attached to the meat. If it appears loose, it indicates that the shrimp is not fresh.
5. No strange odor. Fresh shrimp have a normal fishy smell. If there is a strange or foul odor, it means the shrimp has spoiled.
Although shrimp is delicious, you shouldn't eat too much at once. Don't overindulge!