Abstract: In order to improve the storage stability of chrysanthemum flower powder, the moisture adsorption isotherms of chrysanthemum flower powders from the cultivars ‘Huangshan Gongju’ and ‘Jinsi Huangju’ were determined at 20, 30 and 40 ℃ by gravimetry. The thermodynamic properties, namely net isosteric heat of adsorption (qst), differential entropy (ΔSd), enthalpy-entropy compensation, specific surface area (So) and effective pore size (rp) were also determined from the moisture adsorption data. Results showed that moisture adsorption in chrysanthemum flower powder conformed to type II adsorption isotherms. The Peleg model was found to be the most suitable to describe the water adsorption characteristics of chrysanthemum flower powder, followed by the GAB model. The monolayer moisture content values (Xm, on a dry mass basis) calculated by the GAB model at 20, 30 and 40 ℃ were 0.065 2, 0.062 4 and 0.054 3 g/g for ‘Huangshan Gongju’ chrysanthemum powder; and 0.059 4, 0.058 1 and 0.055 7 g/g for ‘Jinsi Huangju’ chrysanthemum powder, respectively. For both cultivars, qst and ΔSd decreased exponentially with the increase in equilibrium?water content (Xeq). The isokinetic theory indicated the water adsorption isotherm of chrysanthemum powder was an enthalpy-controlled and non-spontaneous process. The So values at 20, 30 and 40 ℃ were 231.22, 221.29 and 192.56 m2/g for ‘Huangshan Gongju’ chrysanthemum powder; and 210.61, 206.04 and 197.35 g/g for ‘Jinsi Huangju’ chrysanthemum powder, respectively. The effective pore size (rp) increased with increasing water content and temperature, ranging from 1.022 to 10.115 nm for ‘Huangshan Gongju’ chrysanthemum powder and from 1.029 to 10.185 nm for ‘Jinsi Huangju’ chrysanthemum powder. This study may provide a theoretical basis to select the proper drying technology and storage conditions for chrysanthemums flowers.

Key words: chrysanthemum powders; moisture adsorption isotherm; thermodynamic properties; mathematical model; equilibrium water content