Oleofoams and emulsion foams stabilized by sodium stearoyl lactylate: Insight into their relations based on microstructure, rheology and tribology

Herein, three types of oil-containing foams, including oleofoams (OF), W/O and O/W emulsion gel foams (EGFs), with high overrun and desirable shaping properties were designed and prepared with sodium stearoyl lactylate (SSL). SSL-based OF and W/O EGFs were stabilized depending on the combination of the crystal adsorption at the O-A interface and viscosity enhancement in the continuous oil phase though the introduction of water droplets influenced the crystal size and distribution, while the dense assembly of oil droplets stabilized by SSL crystals jammed in the channels between bubbles was responsible for the stability and the enhancement in the strength of O/W EGFs. Of particular interest was that the introduction of concentrated air bubbles in oil-continuous foams greatly increased the strength of gel systems. Moreover, the type and water content of foams impacted both the texture and the rheology properties. The presence of three phases gave more length scales to the foaming systems and allowed finer property control through modifying various structural units. Tribological evaluation indicated that all foams had better lubrication properties with lower COF values, and there were obvious differences in the lubrication performance between gels and foams, especially for oil-continuous foams in which dense bubbles exerted influence significantly on the tribological behaviors. Particularly, the property of water-continuous foams was closely linked to emulsions, and the water phase dominated the lubrication ability which could be enhanced by forming patcher of oil films. This work would benefit further to design desired application properties and facilitate innovative development of aerated-foods products.