A Comprehensive Study on Sorption, Water Barrier, and Physicochemical Properties of Some Protein- and Carbohydrate-Based Edible Films

The main aim was to discuss the relation between water vapor transmission rate (WVTR) and moisture sorption isotherms (MSIs) of whey protein (WPI), soy protein isolate (SPI), and carboxymethyl cellulose (CMC) films. MSIs obtained using dynamic vapor sorption (DVS) instrument were fitted to GAB, BET, Oswin, Halsey, and Harkins–Jura models, and examined in detail with Peleg approach. BET and Oswin models had the highest R 2 values (0.999). The MSI’s data were used to assess water vapor barrier interactions between permeability ( P -calculated using WVTR), diffusivity ( D ), and solubility ( S ) properties and to compare their feasibility in P = DS simple equation. D and S were calculated using different approaches of Fick’s second law and Henry’s law. Calculated, measured, and predicted all different P , D , and S presented good operational interchangeability ( r = 0.84–0.95). CMC films had the highest WVTR at 1008.06 g/m 2 day; those of WPI and SPI films were 865.79 and 595.71 g/m 2 day at studied condition. The hydrophilicity of CMC films deduced from its high water vapor adsorption capacity might lead to the lowest D among the studied films. This might result in swelling of film matrix and reduction of film porosity. It was interesting to note that films having the highest S o (128.8 cm 3 /cm 3 cmHg) presented the lowest diffusivity (2.51 × 10 −11 cm 2 /s) with a highest WVTR. Oxygen barrier, mechanical, thermal, and structural measurements were also applied to characterize the films. SPI film was the finest film in terms of its barrier film properties and good film-forming ability.