Catastrophic phase inversion of bigels characterized by fluorescence intensity-based 3D modeling and the formability for decorating and 3D printing

Abstract

In this paper, gelatin hydrogels and glycerol monostearate (GMS)-enhanced ethyl cellulose (EC) oleogels were used as two phases for preparing bigels. The proportion of components in bigels was changed to explore the catastrophic phase inversion of bigels, which was analyzed by textural, rheological, laser confocal imaging, 3D stack modeling of techniques, and the measurement of the hydrophile-lipophile balance (HLB). As the oleogel fraction was less than 40 wt%, the bigel presented as the O/W type, and oil droplets were evenly distributed and stabilized by the gelatin, having the size smaller than 15 μm. When the oleogel fraction was 42 wt%, bigels exhibited the semibicontinuous state due to the critical HLB of 8.23 that water and oil phases both had continuous and dispersed phases concurrently. The 3D model of bigels calculated a sharp increase of droplet sizes to 35 μm in the transition state. The water phase in bigels became the dispersed phase when the oleogel fraction was more than 44 wt%, and GMS was mainly responsible for emulsifying and stabilizing water droplets, and the size of water droplets decreased from 35 μm. Applications of bigels in decorating and 3D printing were discussed combined with physical properties of different types of bigels. O/W bigels containing 40 wt% oleogels could inherit the hardness and formability from gelatin hydrogels and have ideal rheological properties for decorating. W/O bigels with 60 wt% oleogels were more suitable to be used as printing ink for 3D printing, resulting from the strong thixotropy of EC oleogels.