Modulating oxidative stability of zein-stabilized Pickering emulsions via interfacial nanoparticle localization and dual-phase antioxidant synergism: a real-time kinetic assessment by isothermal calorimetry

This study explores the oxidative stability of zein-derived based Pickering emulsions, focusing on the synergistic effects of interfacial particle concentration and phase-specific antioxidant delivery. Emulsions were prepared with varying ZNP concentrations (0.5-2.0%, <i>w</i>/<i>v</i>) in combination with xanthan gum as a co-stabilizer, to which l-ascorbic acid in aqueous phase and α-tocopherol in oil phase were added, individually or in combination. Emulsions with 0.5-1.0% ZNP remained physically stable during 10 days at 40 °C, while increasing ZNP to 2.0% significantly reduced droplet size (22.3 ± 0.55 μm to 16.1 ± 0.38 μm) and enhanced oxidative stability, increasing induction time from 4.07 ± 0.10 × 10⁵ s to 5.15 ± 0.12 × 10⁵ s. Antioxidants further improved the oxidative stability in a concentration-dependent manner, with α-tocopherol outperforming l-ascorbic acid. Notably, co-delivery of both antioxidants produced a synergistic effect, extending induction time to 6.06 ± 0.17 × 10⁵ s and achieving an antioxidant efficiency of 25.04 ± 2.10 at 2.0% ZNP and 30 μM of each antioxidant. Synergism was confirmed by combination index (CI < 1) analysis. Isothermal calorimetry was used for continuous real-time observation of lipid oxidation and provided kinetic parameters including induction time (τ), inhibited and uninhibited oxidation rates (R_inh, R_uni), oxidizability index (O.I.), and antioxidant efficiency (A.E.). These findings establish a novel approach to modulate oxidative stability through dual-phase antioxidant localization and interfacial nanoparticle design in emulsion-based food systems.