Tea saponin improved the physical stability of pea protein cold-set emulsion gel

While plant protein-based emulsion gels have attracted widespread attention, their physical stability remains a challenge. To address this, we improved the physical stability of pea protein isolate (PPI) emulsion gels through the incorporation of tea saponin (TS). Emulsion gels were fabricated by crosslinking PPI-TS complex emulsions with calcium ions. The PPI-TS/Ca²⁺ emulsion gel exhibited a higher storage modulus and superior physical stability than the PPI/Ca²⁺ emulsion gel (i.e., 5.0% PPI and 6 mM Ca²⁺). Increasing the concentration of both PPI and calcium ions led to a more compact gel structure, enhanced gel elasticity and physical stability. Moreover, the structural changes in PPI induced by TS were examined. The increase in free sulfhydryl content, surface hydrophobicity, and intrinsic fluorescence intensity indicated that tea saponin promoted the unfolding of PPI. This unfolding exposed hydrophobic groups, and the addition of calcium ions facilitated the cross-linking of PPI, thereby enhancing the hydrophobic interactions within the protein molecules. These structural modifications facilitated stronger hydrophobic interactions and more efficient cross-linking between protein molecules upon calcium ions addition, ultimately leading to a denser and more robust gel network with improved physical stability. These findings present a promising strategy for the development of stable emulsion gel-based products.