Background : We examined the inorganic compounds, compressive strength, yield, and functional substances of five steam-treated deciduous tree species to address the problem of the low degradation activity of conventional oak trees in the cultivation of Gastrodia elata in indoor facilities.
Methods and Results : With the exception of Ca in cherry blossom tree (CBT), the content of the major inorganic elements (N, P, Mg, K, and Ca) in alternative trees were 1.5 - 3.6, 1.3 - 2.6, 3.3 - 5.3, 4.4 - 7.5, and 0.9 - 3.9 times those in oak (control group), respectively. The content of trace elements (Zn, Cu, Fe, and Mn) were equivalent to or slightly lower than those in oak, depending on tree species. The compressive strength of alternative trees was 9.3%–34.9% lower than that of oak. The compressive strength after steaming was lower in the order CBT (8.0%), mulberry tree (MBT: 7.0%), chestnut tree (CNT: 7.2%), Siebold's crab (SBC: 6.9%), black locust (BLL: 6.1%), and oak (5.4%). The total weight of oak was 893 g in comparison with the 1,107, 902, 952, 813, and 813 g of MBT, CNT, CBT, SBC, and BLL, respectively. The mature tuber and seed tuber ratios were 31%, 34%, 32%, 32%, 34%, and 30%, and 67%, 75%, 68%, 70%, 73%, and 65%, respectively. The yield index increased overall by 1% - 14%. Total weight after steaming increased by 10%, 18%, 14%, 16%, 20%, and 12% in oak, MBT, CNT, CBT, SCB, and BLL, respectively. Mature tuber and seed tuber ratios after steaming increased by 1%, 1%, 0%, 1%, and 2%, and 5%, 3%, 7%, 2%, 5%, and 5%, respectively. There were no significant difference among tree species in drying ratio, hardness, chromaticity for quality comparisons, and steaming. However, the results of functional substance analysis revealed significant differences in gastrodin, gastrodigenin, p-hydroxybenzaldehyde, and ergothioneine according to tree species.
Conclusion : From the above results, we may believed that five tree species including MBT might have useful as alternative to oak when the cultivation of G. elata in Indoor Facilities.