Evaluation of Interactions Between Carboxymethylcellulose and Soy Protein Isolate and their Effects on the Preparation and Characterization of Composite Edible Films
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Interactions between carboxymethylcellulose (CMC) and soy protein isolate (SPI) were assessed to determine their effects on the physicochemical and morphological properties of SPI-based films. The protein-polysaccharide interactions were investigated by measuring zeta potentials, showing a dependence on the pH, ionic strength and polysaccharide concentration. SPI-based films were prepared with different CMC concentrations (0–0.5%) at pH 11 and the pH of biopolymer coacervation (pHc). The addition of CMC improved mechanical strengths of all films, but films prepared at pHc showed a reduction in percentage of elongation at break, becoming more brittle than at pH 11. The water vapor permeability did not show a strict dependence on the CMC concentration or pH, while the oxygen permeability of films prepared at pH 11 decreased with the addition of CMC until reaching a minimal value at 0.375% CMC. These results reveal the significant effects of SPI-CMC interactions on the formation and properties of films, indicating the potential of this approach to better tailor edible films and coatings for specific applications.