Evaluation of emulsion gels and bigels as animal fat substitutes inmulti-material food 3D printing

Abstract

To successfully develop plant-based meat analogs, it is essential not only to mimic the protein content of conventional meat, but to also replicate the structural and functional roles of animal fat. This thesis investigates two approaches for structuring liquid oils, emulsion gels and bigels, for use as fat substitutes in food 3D printing. The study was conducted in two phases. In the first, the rheological properties, printability in single material printing and microstructure of both gels were evaluated. The second investigated their performance in multi-material 3D printing when combined with a pea protein isolate-based ink, using dual and coaxial extrusion techniques. Rheological analyses, including amplitude sweep, shear-viscosity test, frequency sweep, three interval thixotropy test and temperature sweep, revealed distinct differences in behaviours for each gel. The bigel showed higher initial viscosity and greater thermal sensitivity, but also stronger shear-thinning and self-supporting properties. The emulsion gel was softer and less structurally stable. Confocal laser scanning microscopy provided further insights into the gels’ microstructure and phase distribution, supporting the rheological findings. In 3D printing, both gels were printable using the same G-code with the same printing parameters. However, the bigel retained better definition and buildability, and could withstand increased layer heights, where emulsion gel collapsed. In multi-material 3D printing, the bigel maintained structural integrity when printed together with PPI30, in contrast to emulsion gel, which exhibited poor material distribution and inconsistent extrusion behaviour. The bigel also showed superior storage stability, maintaining their form over extended periods at room temperature. The results demonstrate that while both gel systems are potential options for structured fat replacement, bigel offer greater mechanical stability and compatibility for use in food 3D printing. These findings contribute to the development of more realistic plant-based meat analogs and highlight the importance of optimizing both material formulation and printing techniques.