The Effect of CaCl2 on the Gelling Properties of Pea Protein–Pectin Dispersions

The effects of CaCl₂ addition before (PreCa) or after (PostCa) heating pea protein-pectin dispersions on the formed gel's rheological and microstructural properties were investigated. Isothermal titration calorimetry (ITC) revealed that CaCl₂ bound both pea proteins and pectins through a spontaneous exothermic reaction and pectin exhibited a stronger binding affinity to CaCl₂. In PreCa gels, low levels of CaCl₂ (5 and 10 mM) increased the gel elasticity (increase in the storage modulus, G') and their microstructural compactness. However, higher CaCl₂ levels (15 and 25 mM) decreased gels' elasticity, likely due to diminished hydrogen bonds formed in the cooling stage, resulting in gels with larger voids and fewer interconnections between the protein and pectin phases. In PostCa gels, their elasticity increased with the CaCl₂ content, a rheological change associated with the formation of denser microstructures. The addition of 25 mM CaCl₂ decreased <i>β</i>-sheet and increased <i>α</i>-helix and random coil structures. Hydrogen bonding and electrostatic and hydrophobic interactions contributed to gel formation and stability in both PreCa and PostCa gels, whereas disulfide bonds had negligible effects. This study highlights the role of CaCl₂ in modulating pea protein-pectin gels' properties and microstructures for the development of gel-like foods with diverse textures and mouthfeels.