A weird life hack is going around the Internet at the moment: people are adding a small pinch of salt to their coffee, like it's some sort of horrible soup.
The hack was first spread by Twitter user BirdRespecter, who told followers "a tiny pinch of salt in black coffee removes the bitterness almost entirely. I thought this was common knowledge until my coworker looked at me like I had horns for doing this the other day".
"Your tongue has a bunch of taste receptors [...] on it and what it's generally doing is detecting sodium ions crossing a membrane, and you experience saltiness. And with it, though, you also experience some synergistic effects," YouTuber and barista James Hoffman explained in a video. "Generally saltiness can amplify sweetness, for example, and it can also mitigate or reduce bitterness."
Studies have looked into this, confirming it to be true.
"The apparent ability to increase the intensity of other desirable flavours is puzzling as virtually all published psychophysical studies show that [salt] NaCl either suppresses or has no effect on other flavours," one team wrote in Nature in 1997.
"To reconcile this contradiction we have proposed that salts selectively filter flavours, such that unpleasant tastes (such as bitterness) are more suppressed than palatable ones (such as sweetness) thereby increasing the salience and/or intensity of the latter."
For the study, the team added urea (yes, that substance of pee pee fame) in various quantities to a drink containing variable amounts of sugar and salt. All possible combinations of the drinks were then given to volunteers to assess for bitterness, sweetness and "otherness".
"As predicted, there was a selective suppression of the taste components by sodium acetate," the team wrote. "The bitterness of urea was suppressed much more by the salt than was the sweetness of sucrose. Consequently, the sucrose-urea mixtures with added salt were relatively less bitter and more sweet than when sodium acetate was not added."
[H/T: Science Alert]