Physical Stability of Frozen Eggplant: Emphasis on State Diagram, Sorption, Thermal, Mechanical, and Dielectric Properties

The frozen eggplant was studied using absorption isotherms, measured by using saturated salt solution in desiccator chamber (DES) and the Dynamic Vapor Sorption (DVS) instrument. Melting temperature and glass transition temperature were determined by differential scanning calorimetry (DSC), while mechanical properties were determined by a compression test. In addition, dielectric properties were assessed by means of two instrumental chains to cover a wide frequency range of radiofrequencies. Absorption fitting was able to estimate unfreezeable water content, while the dynamic instrument showed a hysteresis between adsorption and desorption, confirming amorphous materials’ presence in the products. Thermograms revealed two phase transition apparent T g III and T g II affected by the plasticizing effect of water. Mechanical properties confirmed the water influence on structures, as Fermi model fitting ( R 2 = 0.984, RMSE = 3.9 N) shown. Dielectric properties were carried out to allow the description of three main dispersion α , β , and γ relaxations. State diagram was developed to show different zones corresponding to possible physical structures.