LAUSR

Abstract Food waste and food protein resources are both worldwide concerns. The understanding of food waste processing and energy cost are important matters. For these, the study of sorption isotherms and thermodynamic are supportive for industries. The present study aims to evaluate the hygroscopicity and isosteric heat by increasing the protein content in cashew apple waste by semi-solid state fermentation using yeast Saccharomyces cerevisiae and determine the sorption isotherms (non-fermented and fermented) at 20, 30, 40, and 50 °C. Furthermore, thermodynamic functions such as the isosteric heat, the differential entropy of desorption, and the surface area from experimental data were also determined. Results show non-fermented and fermented cashew apple waste differ in their composition, mainly, protein content. Upon completion of the drying process, all isotherms raised have a sigmoid shape (Brunauer's type 2 isotherm). GAB model fits well. The samples' monolayers have water activity lower than 0.25 and moisture lower than 0.18 g of H2O/g of dry matter. Water surface values are smaller in the fermented sample than non-fermented. Fermented samples show lower thermodynamic sorption values such as net isosteric heat, isosteric heat and entropy and enthalpy.