Zein-based oleogels: Oil type impact on functionality in plant-based fat alternatives in 3D printing

This study investigates the impact of five widely used food-grade oils (canola, soybean, olive, palm, and coconut) with different fatty acid composition, degree of saturation, and polarity on the structural and functional performance of zein-based oleogels (ZGs) in a 3D-printed meat analogue. ZGs were characterized using confocal microscopy, colorimetry, oil and solvent holding capacity, rheology, differential scanning calorimetry, and Fourier transform infrared spectroscopy. A dual-extrusion 3D printer was used to create model analogues using ZGs. Results indicated that different oil types impacted the color, solvent-holding capacity, rheological behavior, freeze-thaw stability, and secondary structures for ZGs, with unsaturated oils strengthening 3D printing capabilities. ZGs formulated with saturated oils (palm and coconut) exhibited higher crystallization temperatures, was brighter (higher L values), and had more yellow pigments. ZGs formulated with palm oil demonstrated large aggregation behavior via confocal microscopy and heightened G' during temperature and frequency sweeps, which correlated with its significantly lower solvent holding capacity (67.97 ± 1.66) compared to its counterparts. FTIR revealed subtle shifts in protein secondary structures, with PO exhibiting significantly higher alpha helix content (40.1 %) compared to CNO (32.8 %) and SO (34.1 %). These effects are likely attributed to differences in degrees of unsaturation, which influence interfacial interactions between the zein molecules, oil nuclei, and solvent. As this is the first study to apply ZGs as structured fat mimetics in 3D-printed meat analogues, such findings enhance our understanding of ZG structure-function relationships, thus advancing their applications in bioprinted foods.