Optimizing post-harvest processing conditions for Angelica acutiloba roots in Hokkaido: storage temperature and duration

The traditional post-harvest processing method of Angelica acutiloba roots, which involves hanging the roots outdoors after being harvested, is known to promote the conversion of starch in roots into sucrose, thereby increasing sweetness. At the same time, this method increases the dilute ethanol-soluble extract (DEE) content in A. acutiloba roots to meet the standard set by the Japanese Pharmacopoeia 18th edition. However, in Hokkaido, where A. acutiloba has been cultivated in recent years, it is a challenge to practice this traditional post-harvest processing method owing to the risk of freezing. Therefore, it is necessary to determine post-harvest processing conditions to increase DEE content in A. acutiloba roots in Hokkaido. In this study, we cultivated seedlings in plug trays and the open field in Hokkaido and stored the harvested products at various temperatures and durations to determine changes in DEE content. DEE content immediately after harvest was 20.5% in roots from plug-tray seedlings and 27.8% in roots from seedlings cultivated in the open field. DEE content in roots stored at 0 °C increased slowly over 5 weeks, whereas that in roots stored at 20 °C increased rapidly. We found a strong correlation between DEE content and sucrose content, but not (Z)-ligustilide content. Our findings on the post-harvest processing conditions for roots revealed that the optimal post-harvest processing conditions are storage at 0 °C for at least two weeks during which DEE content increases stably, similar to the traditional method.