Comparative Study on the Effect of Calcium Chloride on the Physicochemical Properties of Glycerol- and Sorbi-tol-Plasticized Pea Protein Isolate Films

Ca2+ can boost protein-protein interactions and, if present at an appropriate level, can potentially improve the physicochemical properties of protein gels and films. This study aimed to determine the effect of CaCl2 (0, 0.01 0.025 0.05% w/w) on the optical, water affinity, and mechanical char-acteristics of glycerol (Gly)- and sorbitol (Sor)-plasticized pea protein isolate (PPI) films. The CaCl2 caused darkening and a color shift of the films from yellow to yellow-green. Additionally, de-creased light transmission, particularly in the UV range, and reduced moisture content were observed. The CaCl2 decreased the water vapor permeability (WVP) of the Gly-plasticized film by an average of 20%, with no effect on the Sor-plasticized film. All films were completely soluble in water. The CaCl2 negatively impacted the mechanical integrity of the films, reducing the tensile strength of the Gly- and Sor-plasticized films by ~16% and 14-37%, respectively. Further increases in CaCl2 content (0.1% and 0.2% w/w) led to concentration-dependent cracks, suggesting protein over-crosslinking. In summary, the incorporation of CaCl2 into PPI films did not provide signif-icant benefits and actually worsened key properties such as transparency and mechanical strength. The type of plasticizer influenced how CaCl2 affected some properties of the PPI film.