Tuna is a popular and healthy ingredient in many dishes, but its color can be a telltale sign of its freshness. Grey or brown tuna may not look appetizing, but is it still safe to eat?
In this article, we’ll explore the reasons behind the discoloration of tuna and whether or not it’s still safe to consume. We’ll also delve into the controversial practice of gassing tuna with carbon monoxide to maintain its color and freshness.
Read on to learn more about how to ensure that your tuna is both delicious and safe to eat.
Is Grey Tuna Safe To Eat?
The short answer is that it depends on the shade of grey. Tuna that has turned a dark brown or green color should be discarded immediately, as this is a sign that it has gone bad and may be unsafe to eat.
However, tuna that has turned a light grey color may still be safe to consume. This discoloration is often caused by oxidation, which occurs when the fish is exposed to air. While it may not look as appetizing as fresh, pink tuna, it should still be safe to eat as long as it has been stored properly and hasn’t exceeded its expiration date.
It’s important to note that grey tuna may have a slightly different taste and texture than fresh tuna, so it’s up to personal preference whether or not to consume it.
The Science Behind Tuna Discoloration
Tuna, like many other types of fish, can quickly turn an unappetizing grey or brown color due to oxidation. Fresh tuna, depending on its fat content, ranges in color from pale pink to deep red. The more fat the tuna has, the lighter its color will be. Tuna tends to oxidize quickly, which causes it to turn grey or brown. Even though it may still be relatively fresh at that point, no one wants to eat it because of the way it looks.
To maintain a color that is appealing to consumers, some restaurants and retailers treat the fish with carbon monoxide. The gas reacts with the myoglobin in the tuna, resulting in a stable pigment no matter how old the fish is. Carbon monoxide can even affect tuna that has turned brown, miraculously changing it to a fresh-looking, rosy color. While carbon monoxide preserves the color of the fish, it does nothing to maintain freshness. It is therefore possible to have a piece of appealingly ruby-red tuna that is in reality days—or even weeks—old.
The rainbow effect seen on raw tuna is caused by the reflection of light off muscle fibers, technically known as double refraction or birefringence. It occurs when the muscle fibers are cut crosswise and can be observed for several days after slicing the meat. Light striking the ends of the fibers is reflected in two different directions, appearing to the eye as a rainbow of colors.
While the rainbow effect is harmless and doesn’t offer any indication of how fresh the meat is, there is another color change that is a sign of meat that has passed its prime: the development of a green pigment. Meat with a green cast is contaminated with bacteria and should be avoided.
At Mikuni, they use only grade-one tuna for their sashimi—the highest possible grade based on initial appearance, size and shape, color, texture, and fat content. They purchase both yellowfin and bigeye tuna from trusted sources that they have come to rely on over the years. They embrace a dedication to quality and freshness that simply cannot be surpassed anywhere else.
Grey Tuna: Safe Or Spoiled?
When it comes to grey tuna, the key factor in determining whether it is safe or spoiled is the shade of grey. As mentioned earlier, a dark brown or green color indicates that the tuna has gone bad and should not be eaten. However, if the tuna has turned a light grey color, it may still be safe to consume.
The discoloration of tuna is often caused by oxidation, which occurs when the fish is exposed to air. While this may affect the appearance of the tuna, it does not necessarily mean that it has gone bad. If the tuna has been stored properly and has not exceeded its expiration date, it should still be safe to eat.
It’s important to note that grey tuna may have a slightly different taste and texture than fresh tuna. Some people may find it less appetizing, while others may not notice a difference. Ultimately, whether or not to consume grey tuna is a personal decision based on individual preferences.
The Controversial Practice Of Carbon Monoxide Gassing
One controversial practice used in the seafood industry to maintain the bright red color of tuna is carbon monoxide gassing. This process involves treating the fish with carbon monoxide, which reacts with the myoglobin in the tuna to create a stable pigment that can last for up to a year, regardless of how old the fish is. While this process does not directly impact the safety of the tuna, it does mask any visual cues of spoilage or bacterial growth, making it difficult for consumers to determine whether the fish is fresh or not.
The use of carbon monoxide gassing has been banned in Japan, Canada, and countries in the European Union due to concerns about its potential use to conceal spoiled fish. In the United States, however, it is still a widespread practice that has made its way into supermarkets, fish markets, and restaurants.
While some argue that carbon monoxide-treated tuna is safe to eat, others believe that intentionally masking the true age of a piece of fish should be considered a public safety risk. Additionally, most of the carbon monoxide-treated tuna comes from third-world countries that do not follow safe food-handling laws, which increases the risk of contamination and foodborne illness.
Consumers who are concerned about carbon monoxide-treated tuna are advised to purchase their poke, sushi, and sashimi from trusted restaurants and shops that source their tuna from reputable sources. It’s also important to remember that color alone should not be taken as an indicator of freshness, and that other factors such as smell and expiration date should also be considered when determining whether or not a piece of fish is safe to eat.
How To Choose And Store Fresh Tuna
When it comes to choosing fresh tuna, there are a few key things to look for. First and foremost, make sure the tuna looks moist and shiny, with a deep red or pink color. Avoid cuts that appear dull, matte, or brown, as these can be signs of oxidation and indicate that the fish is not fresh. Additionally, be on the lookout for any dry or brown spots on the tuna, as well as any rainbow sheen, which can also indicate that the fish is past its prime.
When purchasing fresh tuna, it’s best to buy it from a reputable fishmonger with a high turnover rate. This will help ensure that the fish is as fresh as possible. If you’re not sure how to tell if the tuna is fresh or not, don’t be afraid to ask your fishmonger for advice.
Once you’ve purchased your fresh tuna, it’s important to store it properly in order to maintain its freshness and flavor. Thoroughly remove any excess moisture from the tuna steaks with paper towels before storing. Line the bottom of a food protection container with paper towels and place the tuna steaks in a single layer or stack them between paper towels. Cover with another paper towel, seal the container, and store it in the coldest part of your refrigerator (optimum temperature of 31 F). Avoid wrapping the tuna steaks in plastic cling wrap before storing them.
If you need to store fresh tuna for more than a day, pat it dry, wrap it securely in plastic wrap or foil, and store it in the coldest part of your refrigerator on a bed of ice or in a plastic bag filled with ice. Use within 24 hours. If you know the tuna is fresh and has not been previously frozen, you can wrap and freeze it. However, if you’re buying fresh tuna from a grocery store, it’s likely that it has been previously frozen, in which case it’s best to use it immediately.
Safe Cooking Practices For Tuna.
When cooking tuna, it’s crucial to follow safe cooking practices to ensure that it’s not only delicious but also safe to eat. The Food and Drug Administration recommends a minimum temperature of 145 degrees Fahrenheit for fish, including tuna, to eliminate any potential harmful bacteria. This means that you need to be careful not to overcook the tuna, as it can become dry and tough.
To cook a perfect tuna steak without drying it out, one of the easiest methods is to flash fry it at high heat. This can be done on a grill, skillet, griddle, or any other high heat-safe cooking surface. A quick cooking time allows the tuna to retain more moisture, and the caramelized outer sear will also lock in much of the moisture.
It’s important to choose a fresh cut of meat that is thick enough for cooking tuna steaks. Aim for steaks that are at least an inch thick and have no brown spots on the red surface. Before adding the steak, heat the pan to the correct temperature of 425 degrees Fahrenheit, then cook the steak for over a minute. Depending on how raw you prefer the interior, you can cook it for a bit more. Keep in mind that letting the interior reach a higher temperature can toughen the tuna. Therefore, removing the steak from the heat is generally advised when the interior reaches 65 degrees Fahrenheit.
Another safe cooking practice is to properly thaw frozen tuna before cooking it. Sushi-grade tuna has usually been flash-frozen within a couple of hours of being caught. Thawed fresh-frozen tuna generally does not degrade in flavor or texture as compared to fresh off the boat, so do not hesitate to buy it frozen from any reputable market.
It’s always best to cook seafood thoroughly to minimize the risk of foodborne illness. However, if you choose to eat raw fish anyway, one rule of thumb is to eat fish that has been previously frozen. Some species of fish can contain parasites, and freezing will kill any parasites that may be present. However, be aware that freezing doesn’t kill all harmful germs. That’s why the safest route is to cook your seafood.