Kumagawa-Juku Kudzu Starch

Kudzu (Japanese arrowroot; Pueraria montana var. lobata) is a climbing vine of the legume family that grows rampantly in fields and mountains. It is traditionally regarded as one of the seven flowering plants representing autumn and is mentioned in the eighth-century Man’yoshu, Japan’s oldest collection of poetry. Starch has been produced from kudzu roots for centuries and remains a valuable ingredient for food and medicine to this day. When cooking, it is primarily used to make traditional sweets, such as gelatinous kuzu manju and chewy kuzu mochi, or as a thickening agent. As herbal medicine, it is commonly mixed into drinks to improve blood circulation and to alleviate early cold symptoms such as chills and stiffness.

Kumagawa-Juku Starch in Historical Documents
Kudzu starch from Kumagawa-juku has long been renowned for its excellent quality. Wakasako and Wakasa gunkenshi, two books written in the Edo period (1603–1867) about the history of the Wakasa region, confirm that starch made in Kumagawa-juku was sold in the old capital of Kyoto in the seventeenth century. In 1830, the Confucian scholar Rai San’yo (1780–1832) sent starch from Kumagawa-juku to his sick mother in Hiroshima. The accompanying letter included instructions for preparing a boiled mixture of starch and ginger to help moisten the lungs. Rai praised the quality of Kumagawa-juku kudzu starch as more refined compared to starch made in the Yoshino region of Nara Prefecture, another area famous for the product.

Production Process
The high grade of kudzu starch made in Kumagawa-juku can be attributed to the months-long traditional production method and the quality of water used in the process. Production begins in the winter, since the roots must be harvested before the plant expends nutrients on spring growth. After being washed and peeled, chunks of the thick root are crushed and put through a strainer. The resulting mash is then repeatedly soaked in fresh, cold water. Impurities are removed through a filtering process that is performed multiple times until the white substance left behind reaches the desired quality. After settling, the paste-like starch is left to dry, solidifying into a powdery block that can be broken up and sold to customers.