Unravelling the mechanisms behind the stabilization of oil foams using soybean lecithin

Oil foams are emerging as a promising, versatile system in food, cosmetic and pharmaceutical applications. Existing solutions depend on the addition of particles or surfactant crystallization; however, these approaches often require complex processing steps, introduce solid residues that may affect texture, and rely on kinetically trapped interfacial structures that limit reversibility under ambient conditions. Here, we examine the foamability and stability of food-grade, soybean lecithin in oil of different surface tension. We found that edible oil foams can be formed at room temperature only in long-chain triglyceride oils. By combining microscopy, X-ray techniques, and interfacial rheology, we show that the stabilization arises from the formation of inverse lipid bilayers at the air-oil surface, leading to increased surface elastic modulus and dense thin-films that protect the gas bubbles. We also discovered that different self-assembled structures are formed in different oils. These findings uncover a molecular mechanism for non-aqueous foam stabilization under ambient conditions and establish design principles for surfactant-stabilized oil foams, without particle additives or crystallization.