Sweet potatoes, specifically roasted sweet potatoes known as “yakiimo,” have deep roots in Japanese culture with a history spanning over 300 years. The business of selling yakiimo experienced four booms from the mid-Edo period to 1950. The first boom occurred during the Bunka-Bunsei era (1804) to the Meiji Restoration (1868), when sugar was scarce, making the sweet and affordable yakiimo immensely popular.

Following that, from the Meiji era to the Great Kanto Earthquake in 1923, Tokyo’s population growth and the low prices of yakiimo led to increased demand, prompting the emergence of specialty shops. The third boom took place from 1951 to the Osaka Expo in 1970, and the fourth boom has continued since 2003.

The development of yakiimo machines played a significant role in sustaining these booms. The “yakiimo oven” utilizing far-infrared radiation, an electric automatic yakiimo machine, is a remarkable product. With temperature and cooking time settings, it ensures delicious results. The developer of this oven is Gunsho Co., Ltd., based in Tochigi Prefecture. The CEO of Gunsho, who became independent in July 1982, has been involved in the development and sale of vegetable freshness maintenance equipment (mineral ion treatment). The company focuses on developing and selling processing equipment and promotional devices for the distribution industry, particularly mass retailers, and fruit processing plants.

Gunsho currently serves around 4,000 stores nationwide, including major industry players like Aeon and Ito Yokado. In the featured supermarket, the variety known as “Beni Haruka” is credited as the catalyst for the recent yakiimo boom. Its moist texture and sweetness are popular traits, with soft skin and a high sugar scent. With a its natural sugar content of 30 degrees, it remains delicious even when cooled. Other popular sweet potato varieties include Anno-imo and Beni Azuma. Supermarkets display signage indicating the completion of roasting and promote yakiimo at store entrances. Additionally, various manufacturers conduct promotions with tea and sweets.

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