Effects of natural waxes on the interfacial behavior, structural properties and foam stabilization of aerated emulsions

Aerated emulsions have widespread applications in the food industry. However, the poor stability of aerated emulsions remains a major challenge due to their inherent thermodynamic instability. Herein, a novel strategy to improve the foam stability of aerated emulsions using natural waxes was developed. Natural waxes including beeswax (BW), candelilla wax (CLW), carnauba wax (CW) and rice bran wax (RW), the bio-based and sustainable materials, displayed a high efficiency in improving the interfacial behavior, structural properties and foam stabilization of aerated emulsions. Compared with emulsions containing pure palm kernel stearin (PKS), the presence of waxes enhances the elastic modulus (E') of air-liquid interfacial films and the viscosity (η) of the continuous phase. Interestingly, cryo-scanning electron microscopy (cryo-SEM) images revealed that the fat droplet shape was controlled by waxes. These were related to that waxes were conducive to the formation of larger and rigid fat crystals in fat droplets and facilitated effective piercing of the interface, promoting the fat coalescence. Waxes promoted the formation of partial coalescence in the plateau borders and the interface of the aerated emulsions, thus improving the foam stability. Furthermore, whipping experiments showed that the addition of 1.0-2.0 wt% waxes resulted in a shorter optimum whipping time and a higher overrun of aerated emulsions. The microstructure images showed that aerated emulsions with waxes displayed more numerous and uniform air bubbles. Finally, rheology experiments strongly supported that waxes strengthened the interface and network structure of aerated emulsions. Our observations revealed the mechanism of interaction between the natural wax-tuned interfacial behavior and the structure of aerated emulsions.