How do you choose shrimp when buying them? Seeing a blackened shrimp head inevitably leads to the conclusion that the shrimp are not fresh. But does a blackened shrimp head mean they are rotten and cannot be eaten?

If the shrimp head turns black, it may actually be due to the production of melanin by enzymes in the shrimp’s body. Black spots on the shrimp’s surface or a blackened shrimp head don’t necessarily mean the shrimp are rotten or not fresh.

Does blackening shrimp not necessarily mean they are no longer fresh?

The blackening of shrimp is a natural phenomenon. Shrimp contain a substance called tyrosine, which is the main cause of the blackening. The Council of Agriculture has stated that the blackening of shrimp is not directly related to freshness. Tyrosine is found in the shrimp’s head, feet, and blood, and is broken down to produce melanin, causing the shrimp to turn black.

This type of blackening often occurs in the shrimp’s head and feet. When shrimp are removed from their environment, enzymes catalyze the metabolism of tyrosine, which can cause black spots on the shrimp’s head and feet. However, it’s speculated that differences in the amount of melanin produced and the duration of its action may affect the appearance and visual experience of the melanin. Storing fresh shrimp in a frozen state to avoid temperature fluctuations and consume them quickly will result in fresher shrimp.

Are freshly caught shrimp always fresher?

Which is fresher, freshly caught shrimp or frozen shrimp? All food has its best-case scenario. Freshly caught shrimp are certainly fresher, but they should also be consumed quickly. Otherwise, if the shrimp are left to dry after death, the digestive enzymes in the shrimp may cause the meat to deteriorate, and the meat will age over time.

As for frozen shrimp, the timing of freezing also matters. Rapid freezing immediately after catching the shrimp will better preserve the shrimp’s sweetness and texture.

If fresh shrimp cannot be caught, for both flavor and freshness, shrimp that have been individually rapid-frozen at -20°C offer the best quality. That said, in addition to fresh, live shrimp, shrimp that have been quickly frozen and stored immediately after being caught can also be very fresh.

When selecting shrimp, pay attention to three key points:

1. Smell:

Fresh shrimp have a natural, slightly fishy smell, but stale shrimp can have a distinctly rancid or fishy odor, indicating improper storage or excessive storage.

2. Appearance and Color:

Fresh shrimp should appear gray-green or gray-purple, with a naturally curved body. The Fisheries Agency points out that some businesses have used improper chemical additives, such as borax, to bleach shrimp to make them appear fresh, which can cause poisoning if consumed. Avoid shrimp that are too brightly colored or have an unusual smell.

3. Touching the Shrimp:

Shrimp that has been out of water or left out for too long may have the meat separated from the shell, indicating it’s not fresh. Alternatively, feel the shrimp; if it lacks springiness, it may be old.