Scientists discover sixth taste commonly found in certain candy

Food & Drink

By Brooke Kato

Researchers may have discovered a sixth taste.

In addition to sweet, salty, bitter, sour and umami, scientists have named another category of taste that responds to ammonium chloride, a chemical commonly found in Scandinavian candy.

Researchers from USC Dornsife College of Letters, Arts and Sciences found evidence of a sixth taste after investigating the taste buds of normal mice and those of mice that had been genetically modified to not produce the OTOP1 protein, which respond to the sour taste of vinegar or lemon.

Because ammonium chloride can affect acid, the team wondered if the OTOP1 protein played a role in tasting the substance, testing their theory first by observing the responses of lab-grown human cells to both acid and ammonium chloride before testing on the rodents.

“We saw that ammonium chloride is a really strong activator of the OTOP1 channel,” study author and neuroscientist Emily Liman said in a statement. “It activates as well or better than acids.”

The study, published in the journal Nature Communications, sought to fill the gap in past research, which has previously produced evidence for ammonium chloride taste but had not been able to identify the receptor responsible.

The team observed how the taste buds cells generated an electrical response when ammonium chloride was given, finding that the cells with the functional OTOP1 protein responded to the substance, while the modified cells did not.

To further test their results, researchers gave mice an option between drinking plain water and water laced with ammonium chloride while disabling the bitter cells that respond to ammonium chloride.

They found that the rodents lacking the OTOP1 protein did not mind the taste, while the others were repulsed.

“This was really the clincher,” said Liman, whose team also determined that humans were also sensitive to the taste of ammonium chloride. “It shows that the OTOP1 channel is essential for the behavioral response to ammonium.”

Ammonium is found in products like fertilizer and can be toxic, “so it makes sense we evolved taste mechanisms to detect it,” Liman explained.

In other words, that sixth taste — which is present in various species — is a biological trait for survival.

However, further research is necessary to gain a deeper understanding of sensitivity differences between species.