Growing up, most of us learned that there were five basic tastes – sweet, salty, sour, bitter and umami.
But it’s time to rewrite the textbooks, as scientists from the University of Southern California have discovered a new taste.
They claim that the tongue responds to ammonium chloride in such a way that it should be considered a sixth basic taste.
Ammonium chloride – or salmiak salt – isn’t widely used around the world but can be found in salted liquorice.
‘If you live in a Scandinavian country, you will be familiar with and may like this taste,’ said Professor Emily Liman, lead author of the study.
Growing up, most of us learned that there were five basic tastes – sweet, salty, sour, bitter and umami. But it’s time to rewrite the textbooks, as scientists from the University of Southern California have discovered a new taste (stock image)
For decades, scientists have known that the tongue responds strongly to ammonium chloride.
However, until now, the mechanism behind this reaction has remained unclear.
A protein called OTOP1 is known to be responsible for detecting sour tastes, and the team wondered whether ammonium chloride could also trigger OTOP1.
To put this to the test, they introduced the Otop1 gene into lab-grown human cells, so the cells produced the OTOP1 protein.
They then exposed these cells to acid or ammonium chloride, before measuring the responses.
Ammonium chloride – or salmiak salt – isn’t widely used around the world but can be found in salt liquorice
‘We saw that ammonium chloride is a really strong activator of the OTOP1 channel,’ Professor Liman said.
‘It activates as well or better than acids.’
Further tests on mice confirmed that those with the OTOP1 gene avoided ammonium chloride, while those without it didn’t mind the taste.
‘This was really the clincher,’ Professor Liman added.
‘It shows that the OTOP1 channel is essential for the behavioural response to ammonium.’
Given that ammonium chloride isn’t naturally found in many foods, the researchers questioned what the advantage is in tasting it.
Professor Liman suggests that the ability to taste ammonium chloride might have evolved to help us avoid eating harmful substances that have high concentrations of ammonium.
‘Ammonium is found in waste products – think of fertilizer – and is somewhat toxic,’ she said.
‘So it makes sense we evolved taste mechanisms to detect it.’
The researchers caution that this is very early research, but hope their findings will encourage further studies.
‘Who knows? Perhaps ammonium chloride will join the other five basic tastes to bring the official count to six,’ they added.
