# Tororo (food)
**Tororo** (とろろ) is a viscous, creamy Japanese food made by grating certain raw yams, most commonly Japanese mountain yams sold as yamaimo or nagaimo, which release a mucilaginous, sticky substance when grated.[1](https://en.alegsaonline.com/art/100730) It is eaten poured over rice or noodles, stirred into soups, and used as a binder in dishes such as [okonomiyaki](https://www.edgepedia.org/okonomiyaki).[2](https://www.maff.go.jp/e/policies/market/k_ryouri/search_menu/6789/index.html)
| Key fact | Detail |
|---|---|
| What it is | Grated raw yam, producing a sticky, gel-like paste; the name refers to the preparation, not a plant species[1](https://en.alegsaonline.com/art/100730) • [3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html) |
| Main yams | Yamaimo is a general name for Dioscoreaceae yams including nagaimo (Chinese yam), yamato-imo, ichou-imo, and jinenjo[2](https://www.maff.go.jp/e/policies/market/k_ryouri/search_menu/6789/index.html) |
| Signature dishes | Tororo gohan (over rice), tororo soba (over buckwheat noodles), tororo-jiru (grated yam soup), and okonomiyaki batter[2](https://www.maff.go.jp/e/policies/market/k_ryouri/search_menu/6789/index.html) • [4](https://www.justonecookbook.com/nagaimo/) |
| Why it is eaten raw | Yamaimo is rich in amylase, a digestive enzyme that stops working when heated above 75 degrees[3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html) |
| Slimy component | Galactan, a dietary fiber said to lower blood pressure and help remove cholesterol from the blood[3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html) |
| History | Yamaimo has been eaten in Japan since before the Jomon period (roughly 12,000 to 500 BCE), longer than rice[3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html) |
| Regional tradition | Tororo-jiru is served on January 2nd in Tamba-Sasayama City, Hyogo Prefecture, to aid digestion after heavy New Year dishes[2](https://www.maff.go.jp/e/policies/market/k_ryouri/search_menu/6789/index.html) |
## The yams behind tororo
"Yamaimo" (Japanese yam) is not a single species but a general name for yams of the family [Dioscoreaceae](https://www.edgepedia.org/dioscoreaceae), including nagaimo (Chinese yam), yamato-imo, ichou-imo, and jinenjo.[2](https://www.maff.go.jp/e/policies/market/k_ryouri/search_menu/6789/index.html) The varieties differ mainly in water content and stickiness: nagaimo has a higher water content and a crisper texture, while yamatoimo is extremely sticky and makes a substantial tororo when grated.[3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html) • [5](https://www.nippon.com/en/japan-topics/c15313/yamaimo-exceptional-tubers-that-can-be-enjoyed-raw.html) Unlike most tuberous vegetables, these yams can be eaten raw, which is the basis of tororo.[6](https://www.maff.go.jp/e/data/publish/attach/pdf/index-102.pdf)
Growing conditions change the paste. The registered geographical indication Tokachi Kawanishi Nagaimo from Hokkaido owes its high tororo viscosity and crunchy edible portion to a water content of 83.1 percent and a starch content of 12 g per 100 g, traits bred into the seed yams to match the local cultivation environment.[7](https://pd.jgic.jp/en/register/entry/21.html) In the Tamba-Sasayama region, yamato-imo grown locally is called "Yama no Imo" and is dense and very sticky because of the area's climate and long-time selective breeding.[2](https://www.maff.go.jp/e/policies/market/k_ryouri/search_menu/6789/index.html)
## Preparation
Tororo is made by grating the peeled yam raw. The traditional tool is the suribachi, a ceramic mortar with fine radial ridges: sticky yams are first rubbed against the grooves in a circular motion, then ground with a wooden surikogi pestle to produce a heavy, velvety texture.[8](https://www.kikkoman.com/en/culture/foodforum/fundamentals-101/38-3_grinding.html) A fine grater or mortar produces a smoother result.[2](https://www.maff.go.jp/e/policies/market/k_ryouri/search_menu/6789/index.html)
Two practical cautions apply. The grated yam oxidizes quickly and turns brown after peeling, so it can be dipped in vinegar water to prevent discoloration.[3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html) Grating can also make the hands itchy; soaking the yam, or the hands, in vinegar water for about 10 minutes prevents this.[3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html)
## Dishes
**Tororo gohan.** The simplest form is grated yam poured over cooked rice, often seasoned with dashi and soy sauce; the Japanese also pour tororo over rice with a raw egg and a dash of soy sauce for tororo gohan.[8](https://www.kikkoman.com/en/culture/foodforum/fundamentals-101/38-3_grinding.html) • [4](https://www.justonecookbook.com/nagaimo/)
**Tororo-jiru and the New Year custom.** In Tamba-Sasayama City, tororo-jiru, grated Japanese yam mixed with dashi-jiru (soup stock made from iriko, small dried sardines, or bonito flakes), is said to help digestion, and it was served on January 2nd to aid digestion after eating heavy [New Year](https://www.edgepedia.org/new-year) dishes. The dish is eaten on January 2nd as breakfast or lunch depending on the area, and also as a daily meal during the yam harvest season.[2](https://www.maff.go.jp/e/policies/market/k_ryouri/search_menu/6789/index.html)
**Noodles and pancakes.** Grated yam is used as a binding agent for buckwheat noodles, in tororo soba, and mixed into okonomiyaki (Japanese pancake) batter; it can also be used in botan-nabe, a hot pot with boar meat.[2](https://www.maff.go.jp/e/policies/market/k_ryouri/search_menu/6789/index.html) A common tororo soba preparation serves cold soba noodles with grated nagaimo, a raw egg yolk, and sauce.[9](https://www.youtube.com/watch?v=z38wdsGf2bw) Tororo also appears in dressings for sashimi or vegetables.[3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html)
## Nutrition
Yamaimo is rich in carbohydrates, potassium, and vitamin B1, and is described as useful for aiding the metabolism of sugar, regulating blood pressure, and excreting excess salt.[3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html) Its slimy component is galactan, a dietary fiber said to lower blood pressure and help remove cholesterol from the blood.[3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html) In Japan the yam has long been considered nutritious and invigorating, an effect attributed in part to diosgenin, a precursor to the sex hormone.[3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html) The reason the yam can be eaten raw is its amylase content, a digestive enzyme that is deactivated when heated above 75 degrees, so eating it raw preserves the components that aid digestion.[3](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html)
## Commercial and modern forms
Tororo has moved from home grating into packaged products. A Japanese company sells a certified space food version as powdered yam: adding water to the 26 g pouch makes tororo, at 99.3 kcal per pouch, manufactured by Kyokusyoku Co., Ltd. and classified as a side dish; the yam provides mucin, vitamin B1, and potassium.[10](https://humans-in-space.jaxa.jp/en/life/food-in-space/japanese-food/detail/004487.html) Ready-grated tororo is also sold fresh, such as a 60 g pack of 100 percent nagaimo tororo from Maruko Foods.[11](https://www.maruko-f.co.jp/en/products/tororo_kokusan_tororo_nagaimo100.html) In Aomori Prefecture, the Yamase Nagaimo brand sells frozen tororo made by liquid freezing, which preserves the texture, viscosity, flavor, and nutritional value of freshly grated yam; one 80 g pouch serves about two bowls of tororo gohan.[12](https://www.yamase-nagaimo.jp/commodity.html) Regional branding extends to the tubers themselves, with Tokachi Kawanishi Nagaimo registered as a geographical indication product for its tororo quality.[7](https://pd.jgic.jp/en/register/entry/21.html)
## References
1. [Tororo — grated Japanese yam (sticky mountain-yam preparation), Alegsa Online](https://en.alegsaonline.com/art/100730)
2. [Tororo Gohan | Our Regional Cuisines, Ministry of Agriculture, Forestry and Fisheries (MAFF)](https://www.maff.go.jp/e/policies/market/k_ryouri/search_menu/6789/index.html)
3. [Yamaimo / Nagaimo / Yamatoimo (Japanese Mountain Yam), Glossary, Kikkoman Corporation](https://www.kikkoman.com/en/cookbook/glossary/yamaimo.html)
4. [Nagaimo, Just One Cookbook](https://www.justonecookbook.com/nagaimo/)
5. [Yamaimo: Exceptional Tubers That Can Be Enjoyed Raw, Nippon.com](https://www.nippon.com/en/japan-topics/c15313/yamaimo-exceptional-tubers-that-can-be-enjoyed-raw.html)
6. [Japanese yam, MAFF publication](https://www.maff.go.jp/e/data/publish/attach/pdf/index-102.pdf)
7. [Tokachi Kawanishi Nagaimo, Registered GI Products, Japan Geographical Indication](https://pd.jgic.jp/en/register/entry/21.html)
8. [Grinding, Fundamentals 101 Vol. 38 No. 3, Kikkoman Food Forum](https://www.kikkoman.com/en/culture/foodforum/fundamentals-101/38-3_grinding.html)
9. [Nagaimo (Slimy Yam) & Raw Egg Japanese Noodles | Tororo Soba Recipe Test, emmymade (YouTube)](https://www.youtube.com/watch?v=z38wdsGf2bw)
10. [Japanese Yam Tororo | Certified Japanese Space Food, JAXA Human Spaceflight Technology Directorate](https://humans-in-space.jaxa.jp/en/life/food-in-space/japanese-food/detail/004487.html)
11. [Commercially available 60g of Tororo (100% Nagaimo), Maruko Foods](https://www.maruko-f.co.jp/en/products/tororo_kokusan_tororo_nagaimo100.html)
12. [Yamase Nagaimo frozen tororo product page (Japanese)](https://www.yamase-nagaimo.jp/commodity.html)
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*Topic: Encyclopedia › Arts and culture › Food, customs, and everyday culture › Food, cooking and hospitality › Dishes, foods, and foodstuffs › Rice, noodle, pasta, and grain dishes*
*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license