Scientists believe they have identified a new basic taste that’s detectable by the tongue. Joining the ranks of sweet, savory, sour, bitter, and umami, a new study suggests the tongue might also detect ammonium chloride as a basic taste.
Researchers have known for decades that the tongue responds to ammonium chloride, but new research from USC Dornsife has managed to precisely pinpoint the receptors on the tongue that react to it. It’s all thanks to a protein, called OTOP1, that’s found within cell membranes and forms a channel for hydrogen ions moving into the cell.
This is the same receptor that picks up on acidity, which we taste as a sour flavor like lemon juice or vinegar. The researchers hypothesized that the OTOP1 protein might also respond to ammonium chloride since it’s related to acidity too.
To confirm their hypothesis, the team created lab-grown human cells that featured the OTOP1 protein and then exposed them to acid and ammonium chloride. They found that ammonium chloride activated the OTOP1 receptor just as effectively as acid.
Ammonium chloride is often an aversive taste and most likely evolved to help avoid harmful substances, since ammonia is noxious to humans and other animals. However, it is evident that humans can learn to enjoy it, just like how we’ve acquired a taste for spicy or acidic foods. The ammonium chloride flavor is prominent in salt licorice candy, which is popular in Nordic countries, the Netherlands, and northern Germany.
“If you live in a Scandinavian country, you will be familiar with and may like this taste,” Emily Liman, a professor of biological sciences at USC Dornsife and study author, said in a statement.
“Ammonium is somewhat toxic,” she added, “so it makes sense we evolved taste mechanisms to detect it.”
Achieving the official status of a new taste is not an easy feat, however. In 1908, Japanese chemist Kikunae Ikeda identified the chemical basis of a taste he named umami, the meaty or brothy flavor found in food like soy sauce, seaweed, anchovies, miso, fish sauce, Worcestershire sauce, and Marmite. The word can be loosely translated from Japanese as "pleasant savory taste,” although there’s no English word that truly captures its essence.
It wasn’t until decades later that the Western scientific community accepted that umami was an individual salt in its own right, akin to sweet, savory, sour, and bitter.
The study is published in the journal Nature Communications.