Abstract
The effects of CaCl(2) 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 CaCl(2) bound both pea proteins and pectins through a spontaneous exothermic reaction and pectin exhibited a stronger binding affinity to CaCl(2). In PreCa gels, low levels of CaCl(2) (5 and 10 mM) increased the gel elasticity (increase in the storage modulus, G') and their microstructural compactness. However, higher CaCl(2) 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 CaCl(2) content, a rheological change associated with the formation of denser microstructures. The addition of 25 mM CaCl(2) decreased β-sheet and increased α-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 CaCl(2) in modulating pea protein-pectin gels' properties and microstructures for the development of gel-like foods with diverse textures and mouthfeels.