The texture felt at the fingertips from a cup sleeve can change how sourness in coffee is perceived, according to a research finding.
A research team at Chuo University in Japan created two types of sleeves—one made of sandpaper material and the other of kraft paper—and fitted them alternately onto cups holding black coffee at 68 degrees Celsius, then had 92 blindfolded participants drink from them in sequence, the Mainichi Shimbun reported Monday.
The results were published in the latest issue of the international journal Multisensory Research. The experiment was designed by cognitive psychologist Professor Atsunori Ariga, who led the study, to examine the connection between the sense of touch in the hand and taste perception.
Studies on how the color, shape, and material of a cup or glass affect the evaluation of a beverage's taste have existed before. However, cases that isolated the sense of touch felt by the hand alone to verify its effect on taste have been rare. This is because it had been difficult to remove the influence of vision or the sensation of the lips.
Participants who first touched the rough sleeve and then moved to the smooth sleeve perceived the sourness of the second coffee as distinctly weaker. When the order was reversed, this change did not appear.
The research team interpreted this as an associative effect. The explanation is that a rough texture evokes strong sourness, while a smooth texture evokes weak sourness.
When a smooth texture is encountered after a rough one, the impression of weak sourness becomes fixed, and combined with a sensory adaptation effect that dulls sensitivity to sourness through repeated tasting, the coffee is perceived as less sour than it actually is. When the order is reversed, the impression of strong sourness offsets the sensory adaptation effect, resulting in no change, according to the analysis.
"This discovery could serve as a new criterion for choosing a cup or sleeve that suits an individual's taste," Professor Ariga said. "The habit of carrying one's own cup or sleeve could also lead to eco-friendly consumption behavior."
