Sansho Pepper: Japan’s Citrusy, Numbing Prickly Ash Spice

Sansho smells of lime and leaves a tingling numbness on your tongue. It’s Japan’s member of the Sichuan pepper group: the dried, ground fruit husks of the Japanese prickly ash, Zanthoxylum piperitum, and no relation to black pepper. You’ll find it sprinkled over grilled eel and in shichimi togarashi. Most of Japan’s crop comes from one prefecture, Wakayama, home of a variety that fruits in clusters like grapes.

At a glance

The plant and its relatives

Zanthoxylum piperitum is a shrub or small tree, native from China to South Korea and Japan. Japanese sansho is this species, and the Japanese name comes from the Chinese shan jiao.

“Sichuan pepper” isn’t one species. It’s a spice taken from several closely related Zanthoxylum plants. Katzer says China most often uses Z. bungeanum, Z. simulans, Z. planispinum and Z. armatum, even though Chinese product is often labeled Z. piperitum.² So sansho and most Chinese Sichuan pepper are close relatives, but different species. Korea grows the same species as Japanese sansho and calls it chopi. For other members of the group, see Szechuan pepper and timut pepper.

None of these are related to black pepper. The prickly ashes belong to the rue and citrus family.

Which part is used

The aroma and the bite live in the brown fruit wall, not the seeds. The black seeds usually get removed. Katzer calls their texture unpleasant and gritty, “almost like sand between the teeth.”² Japan also uses the fresh young leaves, kinome, both for flavor and as a garnish.

Flavor and the compounds behind it

Japanese sansho has a fresh, pleasant lime fragrance and a well-developed pungency. Zanthoxylum spices in general build slowly to a numbing, almost anesthetic feeling on the tongue. Next to Chinese red Sichuan pepper, sansho comes across brighter and more citrusy, with a slightly softer tingle, though we found no measurement of that.

The tingle comes from alkamides called sanshools, stored in the fruit wall. Katzer reports total amide content as high as 3% in Z. piperitum. The citrus side comes from the essential oil, which reaches up to 4% in Chinese Sichuan pepper and is mostly terpenes.² We didn’t find an oil analysis specific to Japanese sansho to quote.

You’ll often see sansho’s heat compared with chile peppers on the Scoville scale. We found no Scoville measurement for sansho.

Where it is grown

Japan’s sansho comes overwhelmingly from Wakayama Prefecture. Wakayama’s own fruit-tree booklet, drawing on Ministry of Agriculture statistics, gives:¹

The prefecture’s separate profile of budo sansho puts Wakayama’s national share at about 70%, with no year given.³ We found no figure for world production, so there’s no way to check the claim that most of the world’s sansho comes from Wakayama. What the data do show is Wakayama’s dominance within Japan.

Budo sansho

Budo means grape. This Wakayama variety fruits in clusters like bunches of grapes, with large, thick-fleshed berries. The prefecture says it’s thought to have started in the Tenpo era (1830–1844), when wild plants in the Toi area of what’s now Aridagawa town were brought into cultivation, at first as medicine. The town’s Shimizu district is known as its birthplace.³ It’s in season from early May to mid-August, and it’s used mainly for tsukudani and ground as a spice.

History

Sansho’s documented history is thinner than most accounts let on. The budo sansho origin above, from the Wakayama prefectural government, is the oldest dated record we could open.³

Several claims get passed around without a source we could find: that sansho turned up in Jomon-period clay vessels, that it was called naruhajika in the Nara period, that it treated diarrhea in the Heian period, that samurai used it when hunting in the Kamakura period, and that its pairing with eel started then. We don’t present any of them as fact.

How sansho is used

• Grilled eel. Just One Cookbook’s unagi don recipe lists ground sansho as an optional topping and garnishes the bowl with a kinome leaf.⁴
• Shichimi togarashi. Sansho is one of the seven ingredients in the blends of both Yagenbori in Tokyo and Shichimiya Honpo in Kyoto.⁵ Shichimiya says it matters so much that the quality of the sansho decides the flavor of the blend.⁶ PepperScale also lists sansho among the seven, and says the blend’s heat comes almost entirely from the red chile, with sansho adding at most a mild kick.⁷ Nanami togarashi is another name for the same blend. See also nanami togarashi.
• Tsukudani. This is the main use of Wakayama’s budo sansho.
• Leaves. Fresh kinome work as both flavoring and garnish.
• Grilled meats. Sansho flavors teppanyaki meats, though cheaper white pepper often takes its place.

In Western cooking, treat sansho like a citrusy pepper on grilled steak, duck, pork belly and fried foods. Like Sichuan pepper, it’s brightest freshly ground.

Buying and storage

Look for ground sansho with a strong lime scent and a green to greenish-brown color. A dull, dusty smell means it’s faded. With whole husks, pick out any black seeds and thorny bits of stem, which Katzer warns can be harmful if swallowed.² No source gives a shelf life. Buy small jars and keep them sealed, cool and dark.

Health claims

Yagenbori, the shichimi maker, says sansho has long been used as a traditional painkiller and stomach remedy, and that the ripe fruit wall has been used as a crude drug.⁵ That’s a merchant describing tradition, not evidence that it works. We found no source showing that sansho is a meaningful source of vitamin A, B vitamins or minerals in the amounts you’d use, or that it helps bone density, asthma or rheumatism, so we don’t make those claims. For research on the Chinese species, see Szechuan pepper.

Substitutes and comparisons

Chinese Sichuan pepper is the nearest swap, with less citrus and often more numbing. A little grated lemon or yuzu zest can bring the citrus back. See sansho pepper substitutes, Szechuan pepper, shichimi togarashi and Japanese spices.