Impact of physical changes in mushroom on variation in moisture sorption

In this work, physical changes such as protein denaturation, cell membrane integrity, and the viscoelastic relaxation of mushrooms, as induced by drying treatments, were investigated as possible causes of the variation in moisture sorption isotherms (MSIs) and hysteresis. Our investigations involved both experimental and theoretical evaluation of MSIs. Via analysis with the Flory-Huggins (FH) theory, we concluded that 1) the protein denaturation does not significantly affect moisture sorption and hysteresis, and 2) cell membrane integrity only influences on the moisture sorption/water holding capacity at high relative humidity. Additional experiments show that mushrooms exhibit viscoelastic properties, which are temperature and moisture-dependent. As dynamic vapor sorption (DVS) experiments show signs of viscoelastic relaxation, we consider the latter to be the likely determining factor affecting the variations in MSI and hysteresis. The Flory-Rehner theory follows that one needs to include elastic stress into the driving force of drying. For viscoelastic media, a separate model, like the generalized Maxwell model, should describe the stress evolution linked to a drying model.