Yaki-imo Heads South

In Japan, the call of the yaki-imo truck is a sound of winter. Over the past decade the same stone-roasted sweet potato has become a year-round snack in Hong Kong, Bangkok and Singapore. Exports of Japanese sweet potatoes reached about 7,400 tonnes in 2024, and roughly nine out of ten went to just three markets in Asia. This article looks at how a humble street food turned into one of Japan’s quieter agricultural export successes.

From street trucks to supermarket ovens

Yaki-imo means “roasted potato”. The classic method bakes whole sweet potatoes slowly over hot pebbles, which lets the starch turn into maltose and gives the flesh a sticky, custard-like texture. For decades the dish was sold from small trucks that drove through residential streets in autumn and winter.

The format changed in the 2000s, when supermarkets and drugstores in Japan began installing electric roasting machines near the entrance. The smell pulled in shoppers, and the potatoes became an all-season product. The same in-store roaster is the model Japanese retailers later took abroad.

Why the potato itself changed

The modern boom rests on new varieties bred for sweetness and moisture rather than for starch processing.

Growers also cure and store the harvested potatoes for weeks or months, which raises sugar content before sale. That handling know-how is a large part of what buyers abroad are paying for.

Southeast Asia’s appetite

Where the potatoes go

Hong Kong, Thailand and Singapore together take around 90% of Japan’s sweet potato exports. Taiwan and Malaysia are smaller but growing markets. The average export price in 2024 was just under USD 3,000 per tonne, several times the price of sweet potatoes traded within the region.

The retail engine

The biggest driver has been Japanese retailers operating overseas. Pan Pacific International Holdings’ DON DON DONKI stores in Singapore, Bangkok and Hong Kong roast Japanese sweet potatoes in-store and sell them warm by the piece, often among the stores’ best-selling items. Japanese supermarkets and department-store food halls in the region followed with their own roasters.

Why it works

• Familiar food, premium quality — Sweet potatoes are already eaten across Chinese and Southeast Asian cuisines, so consumers do not need to be taught what the product is
• Health image — Roasted sweet potato is seen as a filling, fibre-rich snack with no added sugar
• Theatre in store — The roasting machine and the smell do the marketing
• Warm climate, cold potato — Chilled yaki-imo, eaten like a dessert, suits tropical markets

Risks on the supply side

Japan grows roughly 700,000 tonnes of sweet potatoes a year, and Kagoshima, Ibaraki and Miyazaki account for most of it. Since 2018 a fungal disease called sweet potato foot rot has cut yields in southern Kyushu, and much of the domestic crop still goes to shochu distilling and starch rather than the table. Farmers are responding with disease-resistant seedlings and stricter field hygiene, and warmer summers have encouraged trial planting as far north as Hokkaido.

Shipping is the other constraint. Fresh sweet potatoes are bulky and sensitive to cold damage, so exporters are also developing frozen roasted potatoes and hoshi-imo (dried sweet potato), which travel further and keep longer.

What it means for overseas partners

• Retailers and food-service operators — Japanese yaki-imo has a proven sales model: an in-store roaster, a branded variety name and a clear origin story
• Importers — Supply contracts with producer groups in Ibaraki or Kagoshima can secure named varieties such as Beniharuka throughout the year
• Food manufacturers — Frozen and dried formats open markets beyond Asia, including sweet potato ingredients for desserts and bakery

Conclusion

Yaki-imo shows how a traditional Japanese food can travel when breeding, post-harvest handling and retail presentation work together. The next stage depends on stable supply at home and on formats that can reach markets further away than Hong Kong and Singapore.