Structure of oleogels from κ-carrageenan templates as affected by supercritical-CO2-drying, freeze-drying and lettuce-filler addition

Templates intended for food-grade oleogel production were produced by supercritical-CO2-drying and freezedrying of κ-carrageenan hydrogels (0.4 g/100 g). Supercritical-CO2-drying produced hard (61 N firmness) and shrunk oleogels, which presented 80% oil content and no oil release. Freeze-drying allowed obtaining soft (2 N) oleogels, with 97% oil content but presenting a high oil release (49%). Lettuce homogenate, used as water phase of the hydrogel, acted as inactive filler agent of template network. It allowed reducing shrinkage and firmness (10 N) of supercritical-CO2-dried oleogels, which presented 94% oil content and 5% oil release. In the case of freeze-dried templates, lettuce-filler increased firmness (4 N) but reduced oil release (34%). SEM image analysis highlighted that the physical properties of κ-carrageenan oleogels can be explained based on the effect of drying technique and lettuce-filler addition on the porous microstructure of the dried templates.