Bioactive compound-loaded food-grade bigels: (I) Characterization and study of colorimetry and 3d-printing capability

The aim of this study was to develop bigels based on agar hydrogel and carnauba wax oleogel as carriers of natural chlorophylls for the printing of functional matrices. Four hydrogel/oleogel (HG/OG) concentrations were proposed (80:20, 60:40, 40:60, 20:80). Natural chlorophyll extracts from Arthrospira platensis and Scenedesmus obliquus were selected due to their distinct chlorophyll profiles. All bigels exhibited good structural stability. Confocal microscopy analysis confirmed that increasing the HG/OG ratio led to a phase inversion from O/W to W/O bigels. FTIR results indicated that all bigels were formed through physical interactions between the OG and HG phases. Rheological analyses revealed dominant solid-like behavior (G′ > G″) and pronounced shear-thinning in all formulations, allowing successful extrusion. Increasing oleogel content resulted in a decrease in G′, G″, and viscosity values, affecting the rigidity and flow properties of the systems. Nevertheless, all bigels were suitable for 3D printing, although formulations with up to 60 % oleogel showed better shape fidelity, surface quality, and reproducibility. The coloration of the bigels showed good stability, particularly at higher oleogel ratios and under refrigeration, as indicated by low ΔE∗ values and minimal changes during storage. Additionally, chlorophylls from the S. obliquus extract maintained a more stable hue over time when incorporated into the bigels. This study reinforces the potential of bigels as effective carriers of bioactive compounds, particularly natural chlorophylls, and supports their application in 3D food printing of functional, structured matrices.