What’s behind the Sichuan peppercorn’s numbing, ma, effects?

 

An unassuming restaurant named Da Sichuan Bistro, offers a dish called Manchurian Chicken, which features the Sichuan peppercorn.

Not far from Stanford University is a small, somewhat shabby little Chinese eatery tucked between a massage parlor and a nail salon. Despite its unassuming exterior, Da Sichuan Bistro is locally famous for a dish that is so spicy, a waitress once warned my Caucasian husband, that it ‘makes people call 911.’

The dish is listed rather unassumingly on the physical menu as Manchurian Chicken, but the online menu’s description also includes its audacious subtitle, “CALL 911 CHICKEN.” If you order the CHICKEN, the waitress will probably verify your choice with a raised eyebrow. The dish arrives at your table as a shock to the eyes. At first glance, it is merely a plate piled high with vermillion peppers. You will have to pick through them in order to find morsels of deep-fried chicken encased in a mottled, mahogany-colored batter shell. When you pop a morsel in your mouth, a delicate symphony of flavors meets your tongue —piquant, as promised, but also salty, sweet, earthy and umami all melding together in an unexpectedly balanced way. You reach for another piece—but wait! The umami lingers, and then shifts sharply upwards into a metallic, sweet taste. Surprisingly, your lips feel cooled and begin to tingle slightly, as though shot through with Novocain. It is this unusual flavor, not the spice, that is the true highlight of the chicken. This flavor is the kiss of the Sichuan peppercorn.

Sichuan peppercorn defies traditional flavor descriptors. At once sharp, meaty and citrusy, it neither bites like the familiar, sneeze-inducing black pepper, nor burns the way sweat-inducing chili peppers do. In Chinese, its flavor is referred to as ma, or numbing. In his culinary tome On Food and Cooking, Harold McGee notes that the flavor produces a sensation that is similar to “touching the terminals of a nine-volt battery to the tongue.”

Although it is referred to in different languages as either a peppercorn or chili pepper, the Sichuan peppercorn is actually neither of those things. In English, the word “peppercorn” is reserved for the tiny stone fruit, or drupe, of the Piper nigrum flowering vine. On the vine, they begin as tiny, green fleshy globes. The fruit is harvested, briefly cooked in hot water, and then dried into peppercorns. Their color, shape and flavor depend on the drying method. In the western world, the form we are most familiar with are the black spheres that fill our pepper mills. Chili peppers, on the other hand, are the hollow fruits of plants in the Capsicum family, typically conical in shape but also found as long Pinocchio noses, or squat, irregular barrel shapes. Domesticated over six centuries ago in central America, these fruits begin green but depending on the exact species will ripen to a flashy lipstick red, chocolatey carnelian, or even a pale, whitish jade. They are enjoyed either fresh for their fleshy crunch, or dried and used as a powdered spice. Sichuan peppercorns, however, are neither drupes of climbing vines nor the hollow fruit of spade-leafed bushes. They are berries produced by small trees in the Zanthoxylum family, native to eastern China and Taiwan. Sometimes the berries are used fresh, but it is the dried husks, resembling for all the world little three-dimensional PAC-MAN characters in either green, pink, or a dull mustard yellow, that are typically used in the southern Sichuan style of Chinese cooking.

In addition to being from three different types of plants, the three types of peppers owe their distinct flavors to different chemical pathways. Black pepper owes its bite to piperine, a molecule that interacts with pain-sensing nerve cells in the tongue and activates the heat- and acidity-sensing components of the nerve cells. Combined, this activation generates the characteristic taste and sensation of black pepper. In contrast, the burning feeling imparted by chili peppers is from capsaicin, a molecule that activates only the heat-sensing nerve cells. Normally, they are triggered by physical heat like fire, so when you wave your hands in front of your mouth after eating jalapeño-laden salsa, it’s because your brain thinks your tongue is literally on fire.

Sichuan peppercorn owes its hair-raising effect to yet another molecule called hydroxy-alpha-sanshool. In 2008, it was found that hydroxy-alpha-sanshool excites the same neurons that are targeted by modern anesthetics, hence the numbing sensation. But anyone who’s eaten Sichuan peppercorn will tell you that their flavor isn’t just the cooling ma feeling. There’s also an odd tingling sensation, not unlike the “pins-and-needles” you get in a limb after sitting on it for too long. A different team of scientists identified specific nerve fibers, called D-hair fibers, that are sensitive to hydroxy-alpha-sanshool. D-hair fibers are responsible for abnormal tingling, such as that felt by diabetic patients with nerve damage, explaining the secondary sensation triggered by Sichuan peppercorn. The fibers also explain the delayed sensation of Sichuan peppercorns: they tend to fire about 65 seconds after they’re stimulated. In 2013, a Japanese team wondered exactly what is the rate of that tingling feeling. To investigate this, they hooked up peoples’ fingers with a mechanical vibrator whose speed could be varied. They administered a dusting of ground-up Sichuan peppercorn on the person’s lips, and then asked when the tingling on the person’s lips matched the tingling in their finger. The exact frequency? Fifty cycles per second, on average. In other words, if you can’t get a hold of Sichuan peppercorn, you can simulate at least half its taste by holding a tuning fork buzzing at 50 hertz to your lips while eating.

If the Sichuan peppercorn has piqued your curiosity but Northern California is a trek for you, don’t despair. “CALL 911 CHICKEN” may be unique to Da Sichuan, but the dish’s true name is la zi ji, and it is a revered regional specialty that you should be able to find at any Sichuan restaurant worth its salt. So the next time you go for Chinese, I encourage you to look for the chicken. Look for the numbing, the ma, the umami and the electric. Look for the Sichuan peppercorn.