dynamic vapor sorption properties of gaz-angubin

gaz-angubin is a sweet exudate naturally produced by an insect from the gavan-e-gaz-angubin plant. adsorption and desorption isotherms for a gaz-angubin sample were determined at 15° and 25°c over a range of relative humidity from 0 to 90% using a dynamic vapor sorption system. at different levels of relative humidity, changes in sample mass were continuously measured versus time and described using an exponential model. gaz-angubin exhibited type iii sorption behavior. the sorption capacity decreased with increasing temperature. the sorption-desorption isotherms revealed the phenomenon of hysteresis, in which the equilibrium moisture content was higher at a particular equilibrium relative humidity for the desorption curve than for the adsorption curve. water sorption/desorption isotherms were modelled using the guggenheim-anderson-de boer (gab) model. the gab model showed a good fit to experimental data for water activities of up to about 0.75. it was observed that, for short intervals, the diffusion of water can be described by fickian laws and gaz-angubin showed essentially a fickian diffusion.