When it comes to taste, we’re all different.

While some people prefer the sweet taste of donuts or chocolate, others would jump at the chance to devour some salty fries or some sour candy.

And then there’s the umami flavor often found in meat or soy sauce, and the bitter taste of grapefruit, dark chocolate, or unsweetened coffee.

All these flavors are perceived by us thanks to our taste buds, alongside the influence of the scents picked up by our nose. Our brain puts all these sensations together from the information it gets from receptors in our nose and mouth to deliver what we know as one of these five kinds of taste.

But in a groundbreaking study led by researchers at the USC Dornsife College of Letters, Arts and Sciences, our understanding of taste has suddenly evolved, with a new basic taste confirmed by their work.

Though we’ve long understood the difference between sweet and sour, salty and bitter, it was only in the 1980s that umami was confirmed as a fifth basic taste picked up by humans’ taste receptors.

Though the Japanese scientist Kikunae Ikeda first noticed this meaty, brothy taste – present in some cheeses, meats, and soy-sauce products – in the early 1900s, it wasn’t confirmed until the 1980s.

And now, forty years later, the basic tastes are being expanded again, with the new research – recently published in the scientific journal Nature Communications – proposing ammonium chloride as a sixth basic taste.

That’s thanks to the discovery of protein receptor OTOP1 which detects sour tastes, and the new understanding that the same receptor seems to identify the wholly different ammonium chloride flavor.

But what is this flavor? Well, it’s quite a culturally specific taste, usually attributed to Scandinavian snacks and candies like salt licorice, as the study’s co-author, Emily Linman, explained in a statement:

“If you live in a Scandinavian country, you will be familiar with and may like this taste.”

Salt licorice has a distinct flavor as a result of the salmiak salt, or ammonium chloride, present in its ingredients. And it is this factor that the scientists think explains the OTOP1 receptor’s detection of ammonium chloride too; because like many sour tasting things, it also acidic.

In the lab, the scientists found that lab-grown human cells reacted to ammonium chloride in the same way as with other sour or acidic foods, despite its very different taste.

And similarly, mice who had the OTOP1 didn’t like ammonium chloride when tested in the lab, whereas those without the receptor didn’t avoid it.

In their analysis of their observations, the scientists concluded that the OTOP1 receptor’s reaction to ammonium chloride could have presented an evolutionary advantage, as Liman continued:

“Ammonium is somewhat toxic, so it makes sense we evolved taste mechanisms to detect it.”

So why do many Scandinavians like the ammonium chloride flavor?

Well, just like other flavors that used to signal danger – sour, bitter, and spicy, for example – our understanding of the safety of these foods in modern times allows us to override the warning signals in our brains.

Just as our tastebuds and genetics can adapt, so can we.

If you think that’s impressive, check out this story about a “goldmine” of lithium that was found in the U.S. that could completely change the EV battery game.