Impact of Calcium Chloride Addition on the Microstructural and Physicochemical Properties of Pea Protein Isolate-Based Films Plasticized with Glycerol and Sorbitol

Abstract

Ca2+ can boost protein-protein interactions and, if present at an appropriate level, can potentially improve some physicochemical properties of protein-based gels and films. This study aimed to determine the effects of CaCl2 (0%–0.05% w/w) on the microstructural, optical, water affinity, and mechanical characteristics of glycerol (Gly)- and sorbitol (Sor)-plasticized pea protein isolate (PPI)-based films. CaCl2 caused darkening and a color shift of the films from yellow to yellow-green. Additionally, decreased light transmission, particularly in the UV range, acidification, and reduced moisture content were observed. CaCl2 decreased the water vapor permeability 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. 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 microvoids resulting from protein over-crosslinking and/or coagulation. In summary, the incorporation of CaCl2 into PPI-based films did not provide significant 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-based film.