Why Do Prawns Change Color?

Are you wondering what causes prawns to change color? If you’ve ever bought and cooked prawns, you’ll know their color changes as they cook. Why does this happen? And are there any reasons why raw prawns would change color?

Prawns change color when cooked as the carotenes (pigments) are released from the proteins that cover them. This causes the prawns to change from grey to pink when cooked. Raw prawns may develop black spots or darken in color when exposed to oxygen and are no longer safe to consume.

If you’ve always wondered why prawns change to a beautiful pinkish, orange color when cooked, you’ve come to the right place. We’ll discuss why prawns change color, whether raw or cooked and what you should consider when buying prawns.

Why Do Prawns Change Color When They Cook?

Prawns are interesting crustaceans. Apart from their deliciously soft and sweet flesh, prawns look quite strange while raw. There are wide prawn varieties, and they all differ somewhat in appearance. However, most prawns sold on the market have the same blueish-grey hue to their shells.

What’s interesting is that prawns change completely in color when cooked. The grey shells transform into the most beautiful (and appetizing) pinkish-orange color. But what causes this color change when prawns are cooked?

The pink color cooked prawns take on is thanks to a pigment called astaxanthin. This is the same pigment that causes the pink color in uncooked salmon. So, why aren’t the prawns pink when they are raw too? That’s because the astaxanthin in raw prawns is covered by a protein molecule known as crustacyanin, which conceals the pink pigment.

When the prawns cook, the protein molecules denature (break down). This is why the prawns’ texture also changes as it cooks. As the proteins break down, astaxanthin is released from the proteins, and the pigment is shown in the prawns.

You can tell that the prawns are cooked throughout when the flesh is white, and the shells have a pinkish hue, as this indicates that the protein molecules have been broken down and the prawns are safe to consume.  

While this is the most common reason for prawns changing color, raw prawns can also change color without being cooked. In some cases, this is a cause for concern. So why does this happen?

Why Do Raw Prawns Change Color?

As we’ve mentioned, raw prawns mostly have a greyish color to them. Some prawns have bright red and white coloring, while others are more translucent. However, in some cases, the prawns will change color when removed from the ocean.

For example, you may notice that the prawns become more translucent and develop black spots when they are in your fridge. The black spots show that the prawns have been exposed to oxygen for a period. In this case, the prawns change color like apples after cutting them.

The prawns will secrete an enzyme when exposed to oxygen, resulting in the black spots you can sometimes see on the shells. As the prawns are exposed to oxygen for longer, more black spots will develop.

Fortunately, the black spots aren’t indicative of spoilage. It simply means that the prawns were caught a few hours or days ago. We recommend cooking and eating the prawns soon after purchasing if you notice they have black spots, as these have been out of the ocean for a while.

Another change you may notice in the prawns’ appearance is that the shells start to look somewhat translucent while they are still raw. Unfortunately, this indicates that the prawns are starting to go bad. The flesh will become more translucent as it is broken down by bacteria and enzymes.

The flesh may also pull away from the shell, making it look like the shell is loose around the prawns. In this case, the prawns are spoilt, and you shouldn’t eat them. There are more things you must consider when buying fresh prawns.

How Do You Choose The Best Raw Prawns?

When buying prawns, you must select the freshest prawns available. Seafood starts to spoil soon after being caught, and eating spoilt seafood can cause seafood poisoning. It may lead to you becoming fatally ill. Fortunately, you can prevent this by selecting fresh prawns.

When buying prawns, you can often find them frozen or fresh. Frozen prawns are generally safe to consume unless they show signs of being defrosted and refrozen. Seeing a lot of solid ice in the packet of prawns can signify that they have been defrosted before. In this case, you shouldn’t buy or consume them.

Also, if the prawns have freezer burn, you can usually assume that they have been frozen for a long time. While this doesn’t mean that the prawns are bad, it can cause the meat to be tough and tasteless. Avoid buying frozen prawns with freezer burn for fresh and juicy-tasting prawns.

When buying fresh prawns, there are a couple of other things to consider. First, ask the fishmonger to show you the date on which the prawns were caught, so you know they are fresh. Then, consider these aspects of the prawns:

  • Appearance: Fresh prawns look bright and juicy. The shells should be shiny, and the prawns will look plump.
  • Smell: Fresh prawns smell like the ocean. They should have a fresh and slightly salty smell. If they smell fishy or putrid, they aren’t fresh.
  • Texture: Fresh prawns are plump and stiff. If the prawns look limp or dehydrated, they aren’t safe to consume and are no longer fresh.
  • Storage: The prawns must be kept on ice or in a cold fridge. If you notice the prawns are submerged in icy water, they have been kept outside for too long. Also, prawns should never be kept in the sun.

Once you have established that your prawns are fresh and safe to eat, you can purchase them and take them home for cooking. But how do you keep prawns fresh before cooking them?

How To Keep Prawns Fresh For Cooking

It’s best to use the prawns on the day of purchasing them to ensure they are fresh and delicious. However, if you need to keep them for a day or two, you can place them in a clean bowl in the coldest part of the refrigerator.

If you don’t use the prawns within 48 hours of buying them, it’s best to freeze them. Defrost the prawns overnight in the freezer before using them in your favorite dish.

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Prawns change color as they cook when the pigments are released from the surrounding proteins. The pigments in prawns are the same as those in salmon and give cooked prawns their beautiful pink color. Raw prawns develop black spots when they are exposed to oxygen.