The influence of NaCl on pea proteins based emulgels: From microstructure to macrostructure

The modulation of ionic strength represents an effective strategy to tailor the techno-functional properties of plant protein–based foods. This study investigated the effect of sodium chloride (NaCl) addition (0–0.4 M) to the gelation behaviour of pea protein-based emulgels. Increasing ionic strength up to 0.2 M promoted electrostatic screening, leading to the formation of an elastic, hard texture. This was reflected in larger and more uniformly distributed protein aggregates, along with a significant increase at 0.2 M in hardness (2.73 N) and elastic modulus (4.8 ∙ 10 ³ Pa) compared to 0 M emulgels (1.60 N and 1.36 ∙ 10 ³ Pa). At the molecular scale, 0.2 M enhanced proton mobility within protein- and starch-associated water domains, indicating greater network flexibility during gel formation. In contrast, increasing NaCl concentration from 0.2 to 0.4 M resulted in weakened mechanical properties, with reduced hardness and elastic modulus (2.06 N and 3.7 ∙ 10 ³ Pa, respectively), accompanied by lower proton molecular mobility as the displayed by the NMR population abundance, consistent with network tightening. Large amplitude oscillatory shear rheology revealed an earlier onset of energy dissipation and increased susceptibility to structural breakdown at 0.4 M. Strong correlations (r > 0.93) among springiness, yield point, and ¹H NMR relaxation parameters confirmed that springiness and molecular protons dynamics are driven by the same salt-dependent structural transitions. This study identifies an optimal ionic range for strengthening pea protein emulgels and provides a practical route for designing plant-based gel systems with tailored structure through controlled salt adjustment.