Subway Tuna: How It's Actually Made In-Store
Two Ingredients. That’s It.
Subway’s tuna salad is made from exactly two ingredients mixed together in the restaurant:
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- Canned skipjack tuna (packed in water)
- Mayonnaise
No celery, no onion, no relish, no seasoning. Just tuna and mayo, mixed in a bowl and stored in a cold well. It is one of the simplest protein preparations in all of fast food, and it became one of the most controversial after a 2021 lawsuit claimed the tuna wasn’t actually tuna.
We’ll get to the lawsuit. But first, let’s talk about what actually happens behind the counter.
How Subway Prepares the Tuna
The tuna prep happens during the morning prep shift, usually alongside bread baking and vegetable prep. Here’s the full process:
Step 1: Open the Cans
Subway receives commercial-sized cans of skipjack tuna — typically 66.5-ounce cans (about 4 pounds each). These are standard foodservice cans, not the small consumer cans you’d buy at a grocery store. The tuna is packed in water, not oil.
A prep worker opens the cans and drains the water thoroughly. The more water that remains, the more watery and runny the finished tuna salad will be. Proper draining is the single most important quality control step in the entire process.
Step 2: Add Mayonnaise
The drained tuna goes into a large stainless steel mixing bowl. Then the mayo goes in — and there’s a lot of it.
Subway uses commercial mayonnaise that arrives in large bags or pouches (not jars). The ratio of mayo to tuna is approximately 60:40 by weight — meaning the finished tuna salad is roughly 60% mayonnaise and 40% tuna by mass.
This ratio surprises most people, but it’s standard for commercial tuna salad. The mayo serves as both a binder (holding the tuna together so it’s scoopable) and a flavor carrier. Without enough mayo, the tuna salad would be dry, crumbly, and difficult to portion consistently.
Step 3: Mix
The tuna and mayo are combined using a large spoon or spatula. The mixing is done by hand — there’s no mechanical mixer involved. The target consistency is smooth but not puréed — the tuna should be broken up into small flakes evenly distributed throughout the mayo, with no large chunks or dry spots.
Mixing takes approximately 3–5 minutes per batch. Under-mixing leaves dry pockets of tuna. Over-mixing turns it into a paste.
Step 4: Store and Date
The finished tuna salad is transferred to Cambro containers (food-grade plastic storage), lidded, date-labeled, and stored in the walk-in cooler at 40°F or below.
Subway’s food safety standards specify a shelf life of 2–3 days once mixed. After that, it must be discarded. At busy locations, a batch of tuna salad might last only a single day. At slower locations, it could push closer to the expiration limit.
Portioning: The Ice Cream Scoop
When a customer orders a tuna sub, the sandwich artist portions the tuna using a standardized scoop — essentially an ice cream disher with a specific volume.
- 6-inch sub: One level scoop (approximately 2.5 ounces)
- Footlong: Two level scoops (approximately 5 ounces)
The tuna goes onto the bread and is spread evenly with a gloved hand or the back of the scoop. Unlike deli meats that are laid in precise patterns, tuna is a spread — it gets distributed across the bread surface.
The Lawsuit: “Not Real Tuna”
In January 2021, a lawsuit filed in the Northern District of California claimed that Subway’s tuna was “not tuna” and was instead a “mixture of various concoctions that do not constitute tuna.” The lawsuit alleged that independent lab testing found no identifiable tuna DNA in Subway’s tuna products.
The claim went viral. Headlines like “Subway Tuna Isn’t Really Tuna” spread across social media and news outlets. The story became one of the most widely shared food controversies of the decade.
What Actually Happened
Here’s what subsequent, more rigorous testing found:
The New York Times commissioned independent lab testing in 2021. Their results:
- The lab could not identify the species of fish in some samples
- However, the lab noted that cooking and processing can break down DNA to the point where standard PCR testing (the method used to identify fish species) becomes unreliable
- The tuna is cooked twice — once during canning (at high temperatures for sterilization) and the proteins are further degraded by the mayonnaise’s acidic environment
- The lab explicitly stated that the inability to detect tuna DNA does not mean the product isn’t tuna — it means the testing method has limitations for heavily processed samples
Inside Edition sent samples to a lab that confirmed the samples contained tuna (skipjack, specifically).
Subway commissioned its own testing through an independent laboratory, which confirmed the product as skipjack tuna (Katsuwonus pelamis).
The Lawsuit’s Outcome
The case was dismissed by Judge Jon Tigar in July 2023. The judge found that the plaintiffs failed to provide sufficient evidence that Subway’s tuna was not tuna. The ruling noted that the plaintiffs’ own lab testing was inconclusive, not affirmative evidence of fraud.
An amended complaint was also dismissed in November 2023. The case is effectively dead.
Why the Story Went Viral Anyway
The “Subway tuna isn’t tuna” story persisted long after it was debunked because it fit a pre-existing narrative that fast food is fake and deceptive. The initial headline was more shareable than the follow-up corrections, and most people never read past the headline.
The reality is considerably more boring: Subway’s tuna is canned skipjack tuna mixed with mayo. The DNA testing confusion was a limitation of the testing methodology when applied to heavily processed, cooked, and acidified protein — not evidence of food fraud.
What Skipjack Tuna Actually Is
Some customers hear “skipjack” and assume it’s a lesser or fake type of tuna. It’s not — skipjack (Katsuwonus pelamis) is the most commonly consumed tuna species in the world. It accounts for roughly 60% of all commercial tuna caught globally.
Here’s how it compares to other tuna species:
| Species | Common Use | Flavor Profile | Price |
|---|---|---|---|
| Skipjack | Canned tuna, fast food | Mild, slightly fishy | Lowest |
| Yellowfin (Ahi) | Sushi, steaks | Clean, meaty | Medium |
| Albacore | ”White tuna” cans | Mild, firm | Medium-high |
| Bluefin | Premium sushi | Rich, buttery | Highest ($40+/lb) |
Subway using skipjack is not a quality shortcut — it’s the industry standard for canned tuna. Chicken of the Sea, StarKist, and Bumble Bee all sell skipjack as their primary canned tuna product. It’s the same species you’d buy at any grocery store in America.
The Real Quality Variables
While the tuna itself is straightforward, there are quality variables that affect your actual sandwich experience:
Drain Quality
If the prep worker doesn’t drain the canned tuna thoroughly, the finished tuna salad is watery and runny. It seeps into the bread, making the sub soggy. A well-drained batch vs. a poorly-drained batch is the single biggest quality difference in Subway’s tuna.
Freshness
A batch of tuna salad made that morning tastes notably better than a batch approaching its 2–3 day expiration. The mayo can start to separate slightly, and the tuna develops a stronger fishy taste as it ages in the cold well.
Temperature
Tuna salad that sits in the Bain (the cold well on the sandwich line) too long without being replenished can warm above optimal temperature, especially during a busy lunch rush when the cold well lid is constantly being opened. Warmer tuna tastes more “fishy” and has a less pleasant texture.
Portion Consistency
Unlike sliced meats where every piece is pre-cut to a specific weight, the tuna scoop relies on the sandwich artist using the correct scoop and leveling it properly. A generous scoop vs. a stingy one can mean the difference between a satisfying sub and a bread-heavy disappointment.
The Bottom Line
Subway’s tuna is real canned skipjack tuna mixed with mayonnaise. That’s the entire story. The lawsuit was dismissed, the DNA testing was inconclusive due to methodological limitations, and subsequent tests confirmed skipjack tuna in the product.
Is it gourmet? No. It’s canned tuna and mayo on bread — the same thing millions of people make at home every day. But it is what Subway says it is, and the controversy surrounding it was driven more by viral headlines than by actual evidence of wrongdoing.
The real variable in your Subway tuna experience isn’t whether it’s “real” tuna — it’s whether the prep worker drained the cans properly that morning.