Drying-induced metabolic changes in daylily: A comprehensive analysis of VOC profiles and antidepressant compounds

Daylilies are mellow-colored edible items with significant medicinal value. This study systematically evaluates the changes in the morphology and texture of daylily buds (DLB) dried by three different techniques (vacuum freeze-drying (FD), vacuum drying (VD), and hot-air drying (HD)). FD-DLB retain a more complete microstructure appearance with brighter colors and a better rehydration ability than VD-DLB or HD-DLB. According to the results of electronic-tongue and free amino acid content analyses of nutritional components, FD-DLB retain the freshness, taste, and nutritional value of DLB more than HD-DLB and VD-DLB. GC–IMS detected 28 differential metabolites; among them, the VD-DLB samples contain a relatively high content of 24 volatile components such as methyl hexanoate-D. LC–MS indicates that FD enables the retention of a high level of certain flavonoid components with strong antidepressant activity such as hyperoside, rutin, quercetin. The results of this study confirm that the FD method, which enables a better retention of nutritional and antidepressant active ingredients in DLB samples, exhibits promising potential for industrial application as a drying technology for the manufacture of DLB samples with dual-use value as medicine and food. Therefore, this study contributes significantly to guide future research on optimal methods for the treatment of functional foods.