Moisture sorption characteristics of microalgae Spirulina platensis

In recent times, the microalgae Spirulina platensis has been used as a functional ingredient in several food applications; its process involving drying and storage steps. Moisture equilibrium data for adsorption isotherms of microalgae Spirulina were investigated at 10, 20 and 30ºC and for desorption, at 40, 50 and 60ºC, using the gravimetric static method. The experimental data were analyzed by GAB and BET models. The GAB equation showed the best fitting to the experimental data with R² ≈ 99% and MRE < 10%. The water surface area values calculated by GAB and BET models were very similar. The isosteric heats were determined by application of Clausius-Clapeyron equation to sorption isotherms obtained from the best-fitting equation. The isosteric heat and the entropy of desorption isotherm presented similar behavior, with a sharp change in an equilibrium moisture content of 10%. The enthalpy-entropy compensation theory was applied to the isotherms, indicating that they are enthalpy-controlled.