CELLULOSE-BASED BIGELS AS EDIBLE INKS FOR 3D FOOD PRINTING AND SATURATED FAT REPLACEMENT

Replacing saturated fat in foods requires lipid structuring approaches that provide not only oil binding, but also the mechanical properties needed during processing. In this study, cellulose-based bigels were prepared as edible inks for extrusion-based three-dimensional food printing using hydroxypropylmethylcellulose, methylcellulose, sunflower oil, and glycerol monostearate. The aim was to evaluate the influence of the hydrogel:oleogel ratio and cellulose biopolymer concentration on the bigel structure to obtain semi-solid systems capable of structuring vegetable oil while maintaining shape after extrusion deposition. The aqueous phase was prepared with 2% of hydroxypropylmethylcellulose, methylcellulose, or a 1:1 mixture of both biopolymers. The oil phase was produced with sunflower oil structured by glycerol monostearate. The hydrogel:oleogel phases were combined at 70:30 and 60:40 ratios, resulting in BG_HP70:30, BG_HP60:40, BG_MC70:30, BG_MC60:40, BG_HP-MC70:30, and BG_HP-MC60:40. The bigels were characterized by texture analysis, oil retention capacity, polarized light microscopy, fluorescence microscopy, rheological measurements, and oxidative stability by RapidOxy at 120 °C. After printing, the structures were evaluated for stability using image analysis and texture profile analysis after extrusion and deposition. All formulations were self-supporting and could be extruded through the printer nozzle (diameter: 1.2 mm). However, the cellulose polymer used in the hydrogel phase and the hydrogel:oleogel ratio directly affected the oil retention, oxidative stability, microstructure, and shape stability after deposition. Oil retention ranged from 79.6 to 97.9%, with the highest values for methylcellulose-based bigels, particularly BG_MC70:30 (97.9%) and BG_MC60:40 (95.1%). The 70:30 formulations generally retained more oil than their corresponding 60:40 systems. RapidOxy induction times ranged from 47.1 to 72.0 min, with the longest values observed for BG_HP-MC60:40 (72.0 min) and BG_HP-MC70:30 (65.6 min). Microscopy showed that the best-performing formulations (BG_MC70:30 and BG_HP-MC60:40) had a more continuous network and a more homogeneous distribution of the dispersed phase. Static rheological measurements confirmed the predominance of elastic behavior in all samples, indicating that these systems can resist deformation after extrusion. Overall, the results indicate that cellulose-based bigels are a promising food material for fat replacement in three-dimensional food printing, combining the ability to structure vegetable oils with high oil retention, oxidative stability, and shape maintenance after deposition.