Stabilization models of foams prepared from whippable bigels: Crystal absorption and droplet stability

In this study, three different types of bigel (O/W, bicontinuous, and W/O) were prepared by mixing gellan gum hydrogel and oleogel structured by beeswax in different proportions, and then the bigel was whipped to obtain bigel-based foams. The microstructure of the foam was observed and two foam stabilization models were found. First, the O/W bigel had a crystalline shell on the surface of the oil droplets, and these droplets could accumulate and be adsorbed on or around the bubble surface. The crystalline shell of droplets in O/W bigel might have a positive effect on droplet adsorption on the bubble surface. Secondly, the foams based on bicontinuous and W/O bigels had a crystalline shell on the surface of the air bubbles. An interesting phase transition phenomenon occurred in the 70% oleogel-containing bicontinuous bigel during the process of whipping, which changed from bicontinuous to W/O structure, using crystallization to wrap the bubbles. The overrun of a series of bigels was determined and it was found that the O/W bigel with 40% oil phase and W/O bigel with 10% water phase had the highest overruns of 163% and 83%, respectively. Combined with rheological analysis and 3D printing, it was found that the 60% oleogel bigel-based foam had a high recovery rate, proving that it had great resistance to shear strain and was very suitable for 3D printing. These bigel-based foams can be used as fat substitutes in the food field to significantly reduce calorie intake.