Effect of different kill-green and drying technology on the drying characteristics, bioactivities and volatile profile of Chrysanthemum morifolium leaves

This study elucidates how kill-green (Steaming (ST), Hot air blanching (HWB), Microwave blanching (MWB)) and drying methods (hot-air drying (HAD), vacuum-freeze drying (FD), heat-pump drying (HPD), far-infrared drying (FID), far-infrared combined-heat-pump drying (FID-HPD)) govern quality attributes (color, water state, phenolics and flavor) of C. morifolium leaves. ST achieved superior PPO/POD inactivation ( P < 0.05), with ST-80 s maximizing phenolic retention. Post-steaming, FD preserved native phenolics and α-glucosidase inhibitors; FID enhanced antioxidant products while accelerating dehydration through water cluster disruption (LF NMR confirmed free-to-bound conversion); HAD liberated isochlorogenic acid A via cell wall degradation. Flavor analysis revealed terpenes dominated volatiles (92.12–98.76 %), with FID-HPD maximizing Germacrene D (26.47 %) through abiotic stress-enhanced terpene biosynthesis. Strong correlations linked phenolics/flavonoids to antioxidant capacity, while α-glucosidase inhibition depended on chlorogenic acid-rutin-luteoloside synergy. The integrated ST-FID-HPD approach significantly improved bioactive retention, color profiles, and terpene-rich flavor characteristics, establishing a novel industrial strategy for premium chrysanthemum production. • Kill-green pretreatment enhances the quality of dried C. morifolium leaves. • Steaming (ST) achieves superior enzyme inactivation and phenolic preservation. • Phenolic degradation pathways are distinctly regulated by the drying method. • FID-HPD elevates key terpenes via thermal stress.