Dynamic Vapor Sorption (DVS) Analysis of the Thermo-Hygroscopic Behavior of Arthrospira platensis Under Varying Environmental Conditions

This paper presents a new study and analysis of the thermo-hygroscopic behavior of Arthrospira platensis using dynamic vapor sorption (DVS) system. Thermo-hygroscopic characterization is essential for optimizing the drying process and enhancing storage conditions. Therefore, the objective of this work was to investigate the thermo-hygroscopic properties of Arthrospira (Spirulina) platensis using a dynamic vapor sorption (DVS) system. This thermo-hygroscopic analysis focused on three fundamental parameters, namely: the desorption isotherms, the net isosteric heat of water desorption, and the moisture diffusivity. Desorption isotherms were measured at five different temperatures (25 °C, 40 °C, 50 °C, 60 °C and 80 °C) over a relative humidity range of 10–80%. The desorption isotherm data were fitted to five semi-empirical models: GAB, Oswin, Smith, Henderson, and Peleg. The results indicated that the GAB model provided the best fit for the experimental data. The net isosteric heat of desorption was determined using the Clausius–Clapeyron relation. It decreased from 21.3 to 4.29 KJ/mol as the equilibrium moisture content increased from 0.02 to 0.1 Kg/Kg (dry basis). Additionally, the moisture diffusivity of Arthrospira platensis was estimated based on Fick’s second law of diffusion and the desorption kinetics obtained from the DVS equipment. This parameter varied between 1.04 10−8 m2/s and 1.46 10−7 m2/s for average moisture contents ranging from 0.003 Kg/Kg to 0.191 Kg/Kg (dry basis). Furthermore, the activation energy for desorption was estimated to be approximately 33.7 KJ/mol.