Is there a sixth sense of taste? If so, this is a taste sensation in addition to the established sweet, salty, sour, bitter, and umami. A new study suggests the tongue may also detect ammonium chloride, according to researchers from University of Southern California.
It was not until the 1980s that Japanese scientist Kikunae Ikeda’s proposal, made eighty years previously, that umami is a basic taste. This was the first expansion of the sense of taste since sweet, salty, sour, and bitter were fist characterised.
It now seems there is a sixth basic taste. This comes from neuroscientist Emily Liman and her team, who found that the tongue responds to ammonium chloride through the same protein receptor that signals sour taste.
In terms of diets that could enable people to taste ammonium chloride, this is most likely to be with those from Scandinavian countries. This includes the ingredients that use salmiak salt.
This follows the uncovering of the protein responsible for detecting sour taste. This protein is called OTOP1 and it sits within cell membranes and forms a channel for hydrogen ions moving into the cell.
Hydrogen ions are the key component of acids and the tongue senses acid as sour, as seen with lemonade (rich in citric and ascorbic acids), vinegar (acetic acid), and other acidic foods. The hydrogen ions from these acidic substances move into taste receptor cells through the OTOP1 channel.
It appears that ammonium chloride, as Lab Manager Magazine reports, can affect the concentration of acid (the hydrogen ions) within a cell and this also triggers OTOP1. This was shown by introducing the Otop1 gene into lab-grown human cells to produce the OTOP1 receptor protein. When cells were exposed to acid or to ammonium chloride, it was discovered that ammonium chloride is a really strong activator of the OTOP1 channel.
The reason the taste differs from standard ‘sour’ tastes is because ammonium chloride gives off small amounts of ammonia, which moves inside the cell and raises the pH, making it more alkaline. This results in fewer hydrogen ions.
Animal research showed how the OTOP1 channel in some species seems to be more sensitive to ammonium chloride than in other species. In particular, human OTOP1 channels are very sensitive to ammonium chloride.
The research has been published in the journal Nature Communications. The research paper is titled “The proton channel OTOP1 is a sensor for the taste of ammonium chloride.”
