Oxidation Mechanism in Bigels and Emulgels-Challenges and Solutions

Nutritionally crucial unsaturated fatty acids, especially rich in high omega-3 bonds, are very prone to oxidation. This phenomenon makes oxidation stability a substantial challenge in every formulation, especially those which contain or at some stage of preparation contain water. Bigels and emulgels, which represent promising structured lipid systems for replacing saturated and trans fats in food formulations, pose significant oxidative stability challenges. This review examines oxidation mechanisms in such biphasic systems. Oxidation in bigels and emulgels proceeds through both free-radical-mediated autoxidation and metal-ion-catalysed pathways, with the oil-water interface serving as the primary reaction zone where pro-oxidants concentrate, and lipid substrates become accessible. Structural configuration critically determines oxidative stability, following the sequence W/O bigel > bicontinuous bigel > O/W bigel. The high viscosity of gel matrices provides substantial protection by restricting radical mobility and oxygen diffusion. Mass transfer occurs via diffusion, collision-exchange-separation, and micelle-assisted mechanisms, with association colloids forming localized interfaces that accelerate oxidation. Thermal processing presents particular challenges, as temperatures above 50 °C disrupt most gel structures and accelerate oxidative degradation. Effective protective strategies include interfacial engineering with emulsifiers to reduce oil-water interfacial tension, incorporation of natural antioxidants (e.g., phenolic compounds and tocopherols), and synergistic antioxidant combinations. This review provides a mechanistic framework for formulating oxidatively stable bigels and emulgels suitable for food applications.