Turning gel ratios to engineer 3D-printed hybrid gel-based foamed emulsion

The lack of suitable stabilizers and preparation methods has hindered the development of foamed emulsions with aqueous or oil continuous phase. To address this issue, a simple approach was proposed in this study, which involves whipping hybrid gels to generate foamed emulsions and adjusting the component proportions of the gels to regulate both the physical properties and types of foamed emulsions. Specifically, hybrid gels were prepared by homogenizing the candelilla wax-based oleogel and glycyrrhizic acid-based hydrogel, followed by whipping these hybrid gels to produce foamed emulsions. The influence of the oleogel-to-hydrogel ratios on the physical properties of hybrid gels and foamed emulsions was investigated. Results demonstrated that increasing the ratio from 3:7 to 7:3, and then to 8:2 resulted in a catastrophic phase inversion of hybrid gels, transitioning from O/W to bicontinuous, and finally to W/O type. Foamed emulsions with aqueous continuous phase were derived from O/W type hybrid gels, where partially coalesced oleogel droplets stabilized these bubbles. Moreover, the foamed emulsions with oil continuous phase were prepared by whipping the bicontinuous or W/O type hybrid gels wherein wax crystals anchored on the bubble surface. Small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) test results illustrated that foamed emulsions with aqueous continuous phase demonstrated superior mechanical strength and deformation resistance compared to their oil continuous phase counterparts, making them ideal ink for 3D printing. These findings enrich the formulation of foamed emulsions, enabling their use in developing low-fat, low-sugar foods as well as customized food processing.