Dynamic isopiestic method (DIM): Measuring moisture sorption isotherm of freeze-dried garlic powder and other potential uses of DIM

Moisture sorption (adsorption and desorption) isotherm of freeze-dried garlic powder was measured by static and dynamic isopiestic methods. Isotherms measured by static isopiestic method produced deviations from the dynamic method at the lower and higher water activity ranges. Dynamic method showed that the temperature had more effects on desorption isotherms compared to the adsorption isotherm, and the degree of isotherm hysteresis reduced with the increase of equilibration temperature. The isotherm was fitted with BET, GAB, and Norrish models. Critical evaluations on the physical meaning of the model parameters are presented. The dynamic method has the potential to be used in studying other structural and drying characteristics of foods.