JOURNAL / JAPAN etc.（English）

JAPAN ［Chiba］
Japanese Ingredients for the World’s Top Kitchens ＃23

CURED SWEET POTATOES

Aging Makes All the Difference

2022.12.05

text by Michiko Watanabe / photographs by Daisuke Nakajima / English text by Susan Rogers Chikuba

Though the times are always changing, there are certain timeless ingredients from Japan that will never go out of style. Yukio Hattori, president of Hattori Nutrition College in Tokyo, introduces unique labors of love—items grown and produced with care and integrity by hardworking suppliers across the country.

The eighth-generation heir to a farm in eastern Chiba prefecture, Yudai Ishida always knew that he would carry on his father’s work. But first he earned a degree in business management and worked in public relations to learn marketing. The father-son duo have since expanded their sweet-potato offerings beyond the produce itself to include flavorful steamed and dried packaged items and a confection, too.

“Fresh out of the ground, sweet potatoes are green and unfit for processing,”says Ishida. “We tested the best curing method for preserving their flavor and eventually settled on an earthen cellar we built by hand.” The Ishidas’ highly nutritional, all-natural products include moist-fleshed, steamed sweet potatoes that last for 30 days, and a bite-sized, chewy sun-dried offering that’s sure to win over gummy fans.

土壁の室のなかで、40日熟成させ、糖度を高める。サツマイモの糖度は、収穫後30～60日で、20～30度前後だが、石田農園の土壁の室では、40日で45度以上になる。最高糖度56度を計測したこともあるそうだ。湿度が保たれた室の中の空気は、肌に柔らかい。

石田農園は、生での出荷が９割で加工は１割。紅あずま、紅はるか、シルクスイートを栽培する。サツマイモは養分を吸い上げる力が強いため、同じ品種の連作はしない。

The Ishidas grow three varieties of sweet potato: Beni Azuma, Beni Haruka, and Silk Sweet.

土地の高低差を利用して作られた室。土を掘り出し、屋根を付けた。「大掛かりな設備投資ではなく、あるものを使ってアイデアと工夫で」と湧大さん。

The root cellar is a simple affair, dug out of the earth and with a makeshift roof. Inside, the air is softer.

焼き芋はねっとりとして、繊維が筋のように残ることもない。「シルクスイートの焼き芋は、まるで芋ようかんと言われます」

Steamed Silk Sweets are moist with a smooth consistency almost like jelly.

（写真左）加工前に糖度を上げることで、干し芋は美しい黄金色へ。（写真右）現在、干し芋、焼き芋、スイーツポテトを商品展開。

(photo left) The deep gold of these dried sweet potatoes is owed to the curing process, which converts much of their starch to sugar.
(photo right) A trio of packaged offerings: a confection made with rich cream, and both steamed and dried treats.