Why is Your Tuna Crunchy?

Hint: those shiny flecks aren't bones

Photo by Youjeen Cho on Unsplash

Since I was a kid, I’ve enjoyed a lunch of canned tuna. I love a good tunafish sandwich (especially an open-faced melt), but I also like eating plain tuna straight from the can. Fish contains protein, vitamin D, and heart-healthy omega-3 fatty acids, according to Healthline, and canned fish is an easy way to get their health benefits in an easy form.

Canned fish is certainly having a moment, with a Willy Wonka-type canned fish store attracting tourists in Times Square as an alternative to the M&M Store.

My canned seafood preference is far more humble.

The other day, I bought a few cans of Bumble Bee Prime solid white Albacore tuna. I opened one for lunch and noticed something crunchy. At first, I thought it eas tiny bones, but when I looked, it appeared to be tiny specks of something shiny. Confused, I opened up another can and saw the same thing.

I searched the internet to see if there was a recall, but instead I found out that these shiny bits are actually tiny crystals, called struvite.

Struvite, magnesium ammonium phosphate, are natural minerals that form while the fish is being canned. The magnesium, ammonium, and phosphate naturally found in the fish binds together and forms crystals. Fun fact: struvite is a form of kidney stone in humans, cats, and dogs.

The crystals resemble glass so much, that last year a woman’s TikTok went viral when she filmed what she thought was glass inside a can of Trader Joe’s tuna.

Although they look like glass shards, they’re harmless and naturally occurring and, according to the FDA, the crystals pose no risk to consumers, and the struvite actually dissolves while eating it.

Struvite can be found in most canned fish and can be picked out of it bothers you. They’re also a little fascinating to look at under a magnifying glass, if you have a kid that needs a quick science project.

If you haven’t encountered struvite in your tuna sandwiches, it’s probably been there all the time — you just don’t notice it in a salad with onions and celery and mayonnaise.