Abstract: The aim of this study was to investigate the effect of radiation temperature during far-infrared radiation drying on drying characteristics, microstructure, nutrient components and color of Flos Lonicerae. Drying of Flos Lonicerae was carried out with a far-infrared radiation dryer. The results showed that the increase in radiation temperature could significantly improve the drying rate and shorten the drying time. Only the falling-rate period appeared during the drying process, suggesting that far-infrared radiation drying of Flos Lonicerae is controlled by internal diffusion. The values of effective moisture diffusivity ranged from 1.13 × 10-10 to 4.57 × 10-10 m2/s, which increased with radiation temperature. The increase in radiation temperature could result in the formation of more micro-tunnels of larger size in the structure of dried Flos Lonicerae, which is beneficial to moisture diffusion during the drying process. With increasing radiation temperature, the contents of chlorogenic acid, luteoloside and loganin showed an initial increase followed by a decline. The L* value increased first and then decreased, and the opposite trend was observed for a* and ΔE values. At a radiation temperature of 240 ℃, both high drying rate and a good quality product could be achieved by fixing other drying parameters in this study.

Key words: drying, far-infrared radiation, radiation temperature, Flos Lonicerae, drying characteristics