Sichuan cuisine aficionados have long been familiar with the extraordinary vibrating tingle, akin to a limb waking up after it has fallen asleep, that accompanies a meal spiced up with Sichuan peppercorns, or huajiao.
Now, a new study by a team of researchers has pinpointed the science behind the sensation.
The study, ‘Food Vibrations,’ published earlier this week in the Proceedings of the Royal Society B, finds that the prickly feeling felt on the lips is akin to a vibration of 50 hertz – the same rate at which electrons vibrate on most European and Asian power grids.
A team of researchers at the Institute of Cognitive Neuroscience at University College London were able to discover the number after they found 28 subjects willing to have a Sichuan peppercorn solution applied to their lips. The participants were then asked to compare the tingling sensation on their lips with a vibration mechanism on their fingers. Most chose a rate of 50 vibrations per second.
Likewise, when participants had mechanical vibrations at a frequency of 50 per second placed on their lips, they reported it felt as though they had the Sichuan peppercorn tingle.
“It’s clear when you try Sichuan peppers that it produces a tingling sensation,” said Patrick Haggard, one of the authors of the study. “But we didn’t actually have a full description of what the experience is like. That’s what this paper is about.”
The researchers also found that when they placed the mechanical vibrator on subjects’ lips for an extended period of time to “tire out” the nerves and then applied the pepper solution, the participants perceived the pepper to be less spicy or tingly—which proved the Sichuan pepper activates the same neurons that usually respond to touch.
“It’s a beautiful example of an unusual way of activating the nervous system,” Mr. Haggard said. “The neurons activated normally tell us about light touch, but this isn’t light touch—it’s being activated chemically but the brain experiences as though it’s a vibration.
Previous studies have identified the chemical compound hydroxy-alpha-sanshool as the one most responsible for the pepper’s distinct buzzing, tingling sensation.
The study was not merely an exercise in culinary curiosity: The findings could have implications for further studies about the relationship between taste and touch, and possibly even for the medical treatment of conditions like chronic pain as patients who suffer from it often report a similar tingling, known in medical circles as paresthesia.
The study also suggests that the Sichuan’s pepper mimicry of touch may be its key to boosting flavor, meaning science has confirmed what Sichuanese chefs have known for thousands of years.
“Apparently one of the secrets of Sichuan food is to combine the peppers with chilies and other different flavor to produce some really fantastic combinations,” Mr. Haggard said. “It’s quite an interesting point scientifically.”
– Brittany Hite. Follow her on Twitter @brittanyhite