Tuna is a go-to protein for many – it’s tasty, nutritious, and versatile enough for everything from sandwiches to sushi. But sometimes you take a bite of tuna and instead of a mild, briny flavor, your tastebuds detect something…sour.
So what gives? Why does perfectly good tuna sometimes taste sour?
In this article, we’ll explore the range of reasons your tuna steaks or canned tuna may get that tangy, acidic edge. We’ll look at how mishandling, storage, and cooking errors can create sour flavors. We’ll also cover how to select, store, and cook tuna properly to avoid the dreaded sour bite.
Let’s dive in and demystify why this popular fish can sometimes taste decidedly off.
Deterioration of Muscle Fibers
Freshly caught tuna has a very limited shelf life, One of the main reasons tuna can taste sour is due to naturally occurring deterioration of the muscle fibers after death,
This breakdown process starts immediately after the fish is caught. Enzymes within the tissue break down cell membranes and release acids that build up, giving the meat a sour flavor. Properly bleeding, gutting, and icing the fish right after catch can slow down deterioration. However, some sourness is inevitable.
For commercially caught tuna that isn’t processed quickly, this sour taste is difficult to avoid. Eating tuna within a couple days of catch will provide the sweetest, freshest flavor.
Histamine Poisoning
Another common source of sour tuna is histamine production by spoilage bacteria. This biogenic amine lends an unmistakable tang.
Histamine and other compounds are produced when bacteria convert amino acids in the flesh. Outbreaks of histamine poisoning most often occur with large tunas like albacore. Slow bleeding allows the guts’ bacteria to migrate into the flesh and start synthesizing histamine faster than the fish can be chilled.
Proper handling and refrigeration suppresses bacteria growth. But once present, histamine isn’t destroyed by freezing or cooking. The only way to avoid histamine’s sourness is prevention.
Mishandling During Storage & Transport
From the time it’s reeled in until it reaches your plate, tuna is vulnerable to mishandling that activates spoilage bacteria. Gaps in the cold chain or temperature spikes during storage, transport, and display quickly foster sour compounds.
If tuna lingers too long unrefrigerated before processing, during transit, or at the market, bacteria run rampant. The result is accelerated souring and faster decay. Keeping tuna chilled under 40°F at all times inhibits bacteria and histamine production.
Undercooking the Tuna
Cooking tuna thoroughly to an internal temperature of at least 145°F destroys any harmful bacteria that may be present. Undercooking can allow these bacteria to persist.
Rare seared or lightly smoked tuna may seem appealing. But bacteria concentrated on the surface can survive and produce a sour taste. Cooking tuna until just translucent, flaky, and warm all the way through neutralizes any potential spoilage issues.
Overcooking the Tuna
While raw tuna has risks, overcooking also ruins flavor and makes tuna dry and sour. Excess heat denatures proteins, squeezing moisture from the muscle fibers.
With its lean composition, tuna goes from succulent to cardboard-like quickly. Higher cooking temperatures rapidly accelerate moisture loss. The result is protein that tastes sour and acidic when fried, grilled, or baked too long.
Using Low-Quality Tuna
Starting with poor quality or spoiled tuna makes getting a sour flavor inevitable. Signs of subpar tuna include discoloration, yellowing, dark blood lines in the flesh, dry texture, and an off or fishy odor.
Discolored, aging tuna picked up cheaply at the end of its shelf life is a likely source of sour flavor. For the best results, choose tuna that looks and smells as fresh as possible.
Incorrect Thawing & Refreezing
Thawing frozen tuna incorrectly can seriously damage texture and taste. Slow, gentle thawing in the fridge over 24 hours avoids cell and protein damage.
Aggressive thawing by microwave or soaking causes the formation of large ice crystals that rupture cell walls. This cellular damage releases more sour-tasting compounds upon cooking. Refreezing tuna after thawing intensifies this effect.
Using Old Canned Tuna
Like fresh tuna, canned tuna has a finite shelf life before its flavor goes south. While commercially canned tuna can legally be sold up to five years after processing, the taste deteriorates noticeably after just one to three years.
As the proteins denature and fats oxidize over time, bitterness and sour, metallic flavors develop. So if it’s been sitting in your pantry since before the last presidential election, that tin of tuna is likely past its prime.
Failing to Balance Strong Seasonings
Complementary flavors are important when cooking tuna. Bold marinades and spice rubs containing acid, salt, or umami flavors can make plain tuna shine. But improper balancing can make seasonings overpowering or sour.
Too much acidic citrus or vinegar-based marinade produces an overtly sour tuna flavor. Strong spices and herbs like pepper, chili, and rosemary can also overshadow tuna’s natural sweetness if overdone.
Summary: Handling is Key for Sweet Tuna
While tuna has a naturally short fresh shelf life, proper handling at every step can minimize undesirable sour flavors. Keeping tuna well-chilled, avoiding overcooking, and using high quality, fresh tuna will help prevent a sour surprise.
Master tuna handling basics like careful thawing, strategic seasoning, and not overcooking. Follow storage timelines for fresh and canned tuna. With care, you can ensure that tuna tastes like the sweet, delicate fish it should be.
Why Does Tuna Salad Taste Different From The Deli?
How do you know if canned tuna has gone bad?
The top ways to tell if your canned tuna has gone bad is to check the expiration date, see if the can is leaking, smell it to check for bad odors, see if it’s changed color, check the can for damages, and finally, taste it, which should be your last option if you’re suspicious.
Why does my mouth taste sour?
In some cases, that sour taste could come from something as simple as not drinking enough water. “Dehydration can leave your mouth dry and can alter your sense of taste,” Dr. Tully says. What you can do: Make a point of drinking at least six to eight glasses of water each day to boost your hydration Smoking. Smoking is another common culprit.
How do I know if my tuna is spoiled?
The first and simplest step is to inspect the sell by date or the expiration date. If you’ve gone through these, perhaps it’s time to order takeout. According to Lacademie, raw tuna that has spoiled will appear off-colored, usually with a milky look or with shades of brown. Meanwhile, healthy raw tuna is a deep red or a light pink color.
Does canned tuna smell bad?
However, tuna is a form of fish and therefore has a fishy smell. If you’ve eaten very much canned tuna, you’re probably somewhat familiar with how it typically smells when you open the can. A good way to determine whether your tuna is bad is to take a good whiff of it. You will most likely catch an off odor as soon as you open the can.