iStockphoto / ErikdeGraaf
Umami was the 5th type of taste to be discovered when Tokyo Imperial U. professor Kikunae Ikeda happened upon it back in 1908, joining Sweet, Sour, Salty, and Bitter to make up the five types of taste.
Now, researchers from the University of Southern California‘s Dornsife College conducted research using healthy/normal mice and genetically modified mice without the OTOP1 protein, the protein responsible for the taste response to the sour of lemon and vinegar. What they found is “the tongue might also detect ammonium chloride as a basic taste.”
Where this taste would be most evident, according to the researchers, is in Scandinavian countries where “salt licorice” is a popular type of candy. That’s because salt licorice is made using salmiak salt, or ammonium chloride.
Knowing for many years that taste buds react to ammonium chloride wasn’t enough because scientists didn’t know why those taste buds reacted to it. So this research, into the reactions of taste buds that react to the OTOP1 protein and taste buds modified to not react, appears to have yielded a 6th type of taste according to the press release published this week on Eureka Alert.
Finding A 6th Sense Of Taste
The science of how they pulled this off using mice is pretty incredible. Researchers used a technique that measures electrical conductivity and simulates how nerves conduct signals:
Using taste bud cells from normal mice and from mice the lab previously genetically engineered to not produce OTOP1, they measured how well the taste cells generated electrical responses called action potentials when ammonium chloride is introduced.
Taste bud cells from wildtype mice showed a sharp increase in action potentials after ammonium chloride was added while taste bud cells from the mice lacking OTOP1 failed to respond to the salt. This confirmed their hypothesis that OTOP1 responds to the salt, generating an electrical signal in taste bud cells.
Going deeper, they examined how mice would drink water spiked with ammonium chloride. The mice with OTOP1 protein receptors were turned off by the spiked water but the mice with those receptors disabled didn’t notice it at all.
Ultimately, the reaction to ammonium chloride doesn’t fall within the 5 types of tastes (Sour, Salt, Bitter, Umami, and Sweet). Theoretically, this would be a 6th sense of taste.
However, the scientific community moves at the speed of molasses and it will take countless more studies for the community to even begin to come around to the idea of there being an official 6th sense of taste.