Water adsorption isotherms of microcapsules with hydrolyzed pinhao(Araucaria angustifolia seeds) starch as wall material

摘要

Water adsorption isotherms of microcapsules that use pinhao starch as the wall material and p-carotene as the core material were evaluated. Pinhao was chosen as the raw material because it is primarily composed of starch, and in the literature there are few technological aspects with regard to this polymer. Moreover, this wall material has been previously studied and demonstrated good encapsulation properties. Moisture adsorption isotherms were determined at 10, 20 and 30℃ using the gravimetric method. The Peleg model was used to fit the experimental data. The differential enthalpy and entropy of sorption were calculated using moisture sorption data; both decreased as moisture content increased. The enthalpy-entropy compensation theory was applied to adsorption isotherms and the isokinetic temperature was calculated by plotting the differential enthalpy as a function of differential entropy. We found that the adsorption process was enthalpy-controlled, the T_β (352.61 K) was higher than the T_(hm) (292.77 K), and the process was spontaneous (△G=-470.17J mol~(-1)).