It's tricky to follow your nose when it comes to sniffing out bad tuna. The fish has a natural overpowering scent. But if it has a weird color, has a smell that makes you lose your appetite, is past its shelf-life date or in a puffy can, throw it away. Bad tuna can make you and your loved ones sick.
Fresh tuna steaks are often bright red, but fat content and the species of tuna can change this. Some kinds of bluefin tuna, for example, are more of a watermelon-pink color. During processing, manufacturers treat raw tuna with carbon monoxide to maintain this rosy hue. Otherwise, tuna turns a visually unappealing brown shade. Tuna in cans is already a beige to brown color. Watch for dark brown discoloration around the bone, in tuna steaks. Dark brown, black or green colors -- in fresh or canned tuna -- let you know that the tuna is unsafe to eat.
Tuna has a naturally pungent aroma that's rather meaty. It should smell clean, fresh and like the ocean, whether it's fresh or packed in a pouch or can. Even though the smell of tuna is strong, it shouldn't be unappetizing. If the tuna smells rotten, making you need to plug your nose when handling it, throw it away. An overpowering fishy stench is likely a signal your tuna has gone bad. Never taste any food if you suspect it is rotten or bad. Throw it straight in the trash.
Past Its Sell-By Date
A fresh tuna steak is either flash frozen and thawed, or caught recently and sent directly to your grocer. It doesn't stay fresh for long. Once you get your tuna steak home, eat it within 24 hours. If you picked it up a few ago and haven't had a chance to eat it, it could be bad. Canned tuna has a "sell-by" or "best if used by" date stamped on it. While tuna can certainly be safe to eat past these dates, it's safer just to throw the cans or pouches away. The manufacturer doesn't guarantee freshness after these dates and the tuna could be starting to spoil.
Abnormal Can or Pouch
Before opening up a can of tuna, look for clues that something isn't right. Openings at the seam, dents or a bulging, swollen can signal it's not safe. These abnormalities might be signs of botulism. Although rare, dangerous Clostridium botulinum bacteria from improperly canned foods produce toxins that make you sick. Because foodborne botulism can be fatal, throw the can of tuna away in an outside trash can if you see irregularities. If you have tuna pouches, throw them out if they have been pierced or they are bulging as though filled with gas.