According to The Independent, scientists have discovered that the tongue responds to ammonium chloride as a sixth basic taste, in addition to detecting sweet, sour, salty, bitter and umami tastes.

Research published Thursday in the journal Nature Communications suggests that protein receptors in the tongue that help detect sour tastes respond to ammonium chloride, a common ingredient in some Scandinavian candies.

“If you live in a Scandinavian country, this flavor is familiar to you,” says Emily Lehmann, a neuroscientist at the University of Southern California and study co-author.

Salted licorice has been a popular sweetener in at least some northern European countries since the early 1900s, and its ingredients include salmiac salt or ammonium chloride.

Although scientists know that the tongue responds to ammonium chloride in some way, the specific protein receptors on the tongue that interact with it remain a mystery, despite decades of extensive research.

The process became clear when recent research revealed the protein responsible for detecting sour taste through a protein receptor in the tongue called OTOP1.

This protein is located within the cell membranes of the tongue and forms a channel to transport hydrogen ions – a key component of sour foods – into the cell.

Lemon juice – rich in citric and ascorbic acids – and other acidic foods, such as vinegar, can cause acidity when they reach the tongue.

Because ammonium chloride also affects the concentration of hydrogen ions inside the cell, the researchers wondered if it might also stimulate OTOP1.

To study this, the scientists inserted the gene behind the Otop1 receptor into human cells grown in the lab, where the cells produce the OTOP1 receptor.

The researchers exposed these cells to acid or ammonium chloride and measured the responses. “We found that ammonium chloride is a potent activator of OTOP1,” Dr. Layman said.

A small amount of ammonia has been found to move into the cell from ammonium chloride. Because ammonia is alkaline, it raises the pH; This leads to the reduction of hydrogen ions.

This difference in pH causes hydrogen ions to flow through OTOP1, which the scientists say can be detected by measuring changes in electrical conductance across the channel.

To measure this, the scientists used taste bud cells from normal mice and genetically modified mice that did not make OTOP1, and measured how well the taste cells generated electrical responses when ammonium chloride was introduced.

Although taste bud cells in normal mice showed a sharp increase in activity after the addition of ammonium chloride, mice lacking OTOP1 failed to respond to the organ.

This confirms that OTOP1 responds to ammonium chloride.

The scientists revealed that mice with a functional OTOP1 protein found the taste of ammonium chloride unattractive and did not drink water with the element added.

Researchers suspect that the ability to taste ammonium chloride may have been an adaptation that helped the species avoid ingesting harmful biological materials with high concentrations of ammonium.

“Ammonium is found in waste products — like compost — and is somewhat toxic, so it made sense to develop taste mechanisms to detect it,” Lehmann explained.