It has been established that there are five basic tastes – sweet, salty, sour, bitter, and umami or savouriness, the latter recognised globally in the 1980s.

But what if there were a sixth? A few years ago, scientists suggested the existence of the “taste of fat”, while other studies also looked at the “flavour of starch”.

Now, research suggests that a sixth taste may be linked to the tongue’s response to ammonium chloride.

Salted liquorice is a type of candy popular in Scandinavian culture, particularly in Norway and Sweden. Both loved and loathed, these treats have a flavour that’s hard to describe, at once bitter and astringent as well as salty.

As it turns out, the salt used in these candies is formulated from ammonium chloride, a food additive used in a whole host of everyday products from shampoos to glue.

Taking the form of a white powder, it can be dissolved in water and delivers a slightly acidic taste, which is why it is also used as an acidifier in breads, olives, and certain canned vegetables.

According to science, this could be a sixth taste for humans. Researchers at the University of South Carolina have identified ammonium chloride as an element that can trigger a response of the taste buds to create a connection with an acidic flavour.

In other words, it’s not ammonium chloride itself that would be defined as a sixth basic taste, but rather, its ability to trigger a particular sour taste on the tongue.

While the scientists classify this discovery as a new “flavour”, according to their results published in the journal “Nature Communications”, this does not mean it’s universally regarded as a pleasant taste.

“Most vertebrate species find the taste of ammonium aversive, which serves, in part, to protect them from eating waste products and decaying organic material,” the authors pointed out.

Just as the fifth emblematic taste, umami – originally associated mostly with Japanese cuisine – required years of scientific research to be truly considered a new taste in its own right, it’s a safe bet that further work will need to be carried out to investigate the action of ammonium chloride on the taste buds.

Back in 2016, a sixth flavour related to starchy foods had already been proposed. The theory was that if pasta is so popular, it’s not just because of the carbohydrates present; for a long time, it was thought that the transformation of starch into sweetness through saliva was the main gustatory mechanism.

But in fact, volunteers who took part in one experiment identified a particular taste in these complex carbohydrates, a kind of “starchy” flavour, according to researchers at Oregon State University.

Meanwhile, a 2015 study from Purdue University in Indiana studied the taste of fat and categorised it as a sixth basic taste called “oleogustus” – although its authors noted that consumers often confused it with sour flavours.