There is a very easy way to distinguish a fresh uncooked shrimp from a cooked one: its colour. If you’ve ever cooked shrimp before, you will have noticed this colour transformation. The shrimp will convert from a blue, translucent colour into a white with pink!.
The same happens to lobster as well as crab, a beautiful colour transformation. And behind all of this: fascinating food chemistry!.
And what’s better, it’s not just that transformation going on. Not only does the color change, but so does the shape. We’ll talk about three processes here: the shrimp curling up when they’re cooked, the color change from blue to pink, and the color change from clear to white.
As a seafood lover I’m sure you’ve noticed that raw shrimp have a grayish almost translucent appearance. Yet once they hit the heat, they turn a vivid orangey-pink. What causes this dramatic color transformation?
It comes down to a naturally occurring pigment called astaxanthin When shrimp are cooked, this pigment is released from its bound form and becomes visible The more astaxanthin present, the deeper the orange hue.
In this article, we’ll explore the science, benefits, and implications of astaxanthin in shrimp. Read on to finally understand the reasons behind shrimp’s tendency to turn orange during cooking.
What is Astaxanthin?
Astaxanthin is a fat-soluble carotenoid and powerful antioxidant It’s what gives salmon, lobster shells, crab shells, and shrimp their characteristic reddish-orange coloration
Astaxanthin is produced by microalgae, which form the base of the aquatic food chain. Tiny crustaceans called krill eat the algae, accumulating astaxanthin in their tissues. Shrimp then consume the krill, further concentrating the pigment.
Astaxanthin helps protect the cells of marine organisms from oxidation and damage by UV light. It also aids in immune response and development.
The Science Behind Shrimp’s Color Change
In its natural state, astaxanthin is bound to proteins in shrimp flesh and shells. This makes the pigment essentially “invisible” to our eyes, so the shrimp appear more translucent gray or green.
However, when shrimp are cooked, the proteins holding the astaxanthin begin to break down due to the heat. As the pigment is released from the proteins, its vivid color becomes visible. The more astaxanthin present, the more intense the orange-red hue.
If shrimp are overcooked for too long, the proteins can denature entirely, allowing most or all of the astaxanthin to leach out. This results in rubbery, intensely orange shrimp that are unappetizing.
Why Farm-Raised Shrimp are Extra Orange
You may have noticed that shrimp from aquaculture operations tend to be more deeply colored than wild shrimp. This orange hue is directly linked to astaxanthin levels.
Farmers actually add astaxanthin supplements to the feed pellets they give their shrimp. The goal is to achieve the desired reddish-orange that consumers expect.
Wild shrimp get astaxanthin solely from their natural diets. So their color depends on factors like the carotenoid content of their food sources.
Health Benefits of Astaxanthin
Astaxanthin isn’t just for looks – it also delivers some impressive health advantages:
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Powerful antioxidant – Shown to be 6,000x stronger than vitamin C! Helps fight cellular damage.
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Reduces inflammation – Various studies show it lowering inflammatory markers like c-reactive protein (CRP).
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Boosts immunity – Increases activity of natural killer cells and T-cells.
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Heart health – Decreases LDL cholesterol and blood pressure in clinical trials.
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Eye and brain health – Crosses the blood-retinal and blood-brain barriers to provide antioxidant protection. Also shown to improve blood flow.
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Anti-aging – Combats UV sun damage when applied topically and wrinkle reduction.
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Endurance – Improved muscle recovery and stamina in athletes.
Of course, moderation is key as with any bioactive compound. But for most people, consuming shrimp and other astaxanthin-rich seafood 2-3 times per week can provide health benefits.
Tips for Preventing Overly Orange Shrimp
Now that you understand why shrimp change color, here are some tips for avoiding unappetizing orange shrimp:
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Purchase fresh, wild-caught shrimp when possible. They will have more moderate astaxanthin levels.
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Avoid pre-cooked, frozen shrimp which often contain coloring additives.
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Don’t overcook shrimp. Cook just until opaque and slightly pink – about 2-3 minutes for medium shrimp.
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If boiling shrimp, remove them from the pot immediately after cooking through. Extended boiling intensifies color.
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Soak peeled cooked shrimp in milk or lemon juice to dilute color.
When Orange Shrimp Indicate a Problem
While astaxanthin accounts for most instances of orange shrimp, there are a couple scenarios where it can signal issues:
Sulfite Dip
Some imported shrimp producers use sulfite dips before freezing to prevent melanosis (black spotting). The sulfur dioxide bleaches shrimp, allowing their natural colors to emerge. This can result in an unnaturally bright orange that is unappealing.
Bacterial Growth
Shrimp flesh can also take on an orange tint when spoilage bacteria are present. This usually occurs in thawed, previously frozen shrimp. Fresh shrimp should not turn orange before cooking.
In these cases, it’s best to avoid consuming the shrimp. Stick to fresh, sustainable sources and proper handling methods.
The Takeaway on Shrimp’s Color Transformation
We’ve cracked the case on the science behind shrimp’s tendency to turn orange during cooking. Now you know it comes down to astaxanthin, a carotenoid with some great health benefits.
While an intense orange color may not be the most appetizing, moderate hues are perfectly normal and safe when using quality shrimp. Just be sure not to overcook them!
Next time you fire up a shrimp dish, you can appreciate the fascinating chemistry behind its changing colors. Pass on the knowledge to awe your dinner guests as well.
Shrimp turning from translucent to white
Raw shrimp aren’t only blue when raw, they are also translucent. You seem to be able to watch into the shrimp slightly. During cooking this translucency changes in a white colour, as it does for many other (white) fish.
The process that causes this change in color is the same as the process that makes an egg white turn white when boiled or cooked. Proteins are heat sensitive. Proteins tend to be folded up in all sorts of complex configurations (helices, curls). But when they are heated to high enough temperatures they can uncurl and extend.
It is not just heat that can cause this transformation from translucent to white. Acids can do the same by denaturing the proteins. It is a similar process going on but caused by acidity instead of heat. You use this phenomenon when making ceviche, which is essentially fish ‘cooked’ in acids such as lemon juice.
When you cook shrimp it is not just the colour that changes, the shape changes as well. Once the shrimps starts heating up considerably, they will start to curl up. If you overcook them they will continue to curl up into tight little balls. The texture will be off and not as juice and soft anymore. You’d want to avoid getting to this stage.
No specifics have been given about what happens here, but it probably has something to do with the shrimp’s muscles contracting. Just like a piece of meat will shrink, so does a shrimp. But because a shrimp’s muscles are built very differently than those of a chicken or beef, it will curl up on its own if it is allowed to. Cutting a shrimp in the right places can prevent curling up.
Once more, proteins are very important here because shrimp flesh is mostly made up of them. These proteins curl up and bind less water causing the product to shrink.
From blue to pink – How the colour transforms
Colour is an important part of most foods, but shrimps change color in such a big way. Food turning brown is very common, thanks to the Maillard reaction, caramelization or enzymes. Those reactions are very different from a chemists perspective compared to the shrimp’s colour transformation.
It’s more likely that what’s happening in shrimp is like how fruit changes color when it’s ready to be picked. As they ripen, they lose most of their green color, which comes from chlorophyll. This is because chlorophyll hides many other colors as well. g. in oranges).
Even an uncooked raw shrimp contains the molecule that makes it pink. This molecule is astaxanthin which actually belongs to the group of carotenoids. There are a lot of molecules in this group. Carotene, the molecule that turns an orange carrot, is also in it.
However, in raw shrimp this astaxanhin is bound to proteins forming a complex called crustacyanin. Because of this, the molecules that are stuck together look blue. Light can’t reflect in the right way to make them look pink.
When shrimp are cooked the protein denatures (it unfolds and changes shape) due to the high temperatures. As a result, the astaxanthin is no longer bound and now reflects light in a different way, turning the shrimp pink! This color difference makes it easy to tell if a shrimp has been heated or not: raw = blue, heated = pink.
The temperature at which the colour change happens isn’t known exactly. Time and temperature are likely to work together to tell if the protein has broken down enough for the shrimp to turn pink. This depends on the exact composition of the shrimp. Also, not all proteins will break down at the exact same time.
Why do shrimp turn pink when they are cooked?
Why do shrimp turn orange?
Shrimp turn orange due to a pigment called astaxanthin. This pigment is produced by algae and other organisms that shrimp eat. When shrimp consume these organisms, astaxanthin accumulates in their shells and flesh, giving them the characteristic orange color. The amount of astaxanthin in shrimp can also vary depending on their diet and environment.
What are the side effects of eating shrimp?
Shrimp allergy can be identified from signs and symptoms that appear after consuming shrimp or smelling it, such as itching, the appearance of red plaques on the skin, swelling in the face, especially in the eyes and mouth, and in the throat creating the feeling of a lump in the throat.
Why do shrimp turn brown?
Food turning brown is very common, thanks to the Maillard reaction, caramelization or enzymes. Those reactions are very different from a chemists perspective compared to the shrimp’s colour transformation. Instead, what is going on in shrimps is probably most similar to the colour change that happens when fruit ripen.
What color does shrimp turn when cooked?
Thanks to the Maillard reaction and caramelization, most foods cook to an enticing brown hue. However, the color shift in crustaceans like shrimp is a quite different phenomenon. S hrimps are translucent and light blue when they are fresh. Their color changes to a tasty brilliant orange when they are cooked.