Adsorption isotherms and some thermodynamic properties of multifloral bee pollen at different conditions

Abstract

The aim of this study was to reveal the moisture adsorption properties of multifloral bee pollen and determine some properties of adsorbed water at 15, 25, and 35 degrees C temperatures. The adsorption characteristics of bee pollen were evaluated by the BET, Caurie, GAB, Halsey, and Smith models. According to the results, while the equilibrium moisture content was 0.90-43.58 g/100 g, the monolayer moisture content calculated with the BET and GAB models was 4.91-6.05 g/100 g. The water adsorption of bee pollen showed Type II characteristic. The fitness of models can be ordered as BET > Caurie > GAB > Halsey > Smith at 15 and 25 degrees C according to P% values and the Caurie model was the best for representing moisture adsorption by bee pollen at all temperature and water activity levels. Additionally, the surface area of adsorption, the number of adsorbed monolayers, and the amount of total adsorbed water substantially decreased with the temperature increased from 15 to 35 degrees C. The net isosteric heat of adsorption was between 5.47- (-1.21) kJ/mol and the moisture absorption of bee pollen occurred as spontaneous because of increment G < 0.