Formation and characterization of oleogels obtained via direct dispersion of ultrasound-enhanced electrospun nanofibers and cold milling

Oleogels are semi-solid lipid-based materials designed to replace solid and semi-solid fats in foods, cosmetics, and pharmaceuticals. A new method for oleogel preparation through nanofibers has opened new possibilities for polymers from synthetic and natural origins previously considered inadequate for oleogel preparation. However, the obtained oleogels were made from conventionally electrospun nanofibers, where the production process still has limitations or the oleogel preparation process required different steps, such as use of organic solvents and extensive drying steps. In this work, we present a new organic solvent-free method for preparing oleogels using nanofiber mats of polyethylene oxide obtained with an ultrasound-enhanced electrospinning (USES) device. After dispersing nanofibers in oil followed by a cold-milling process, we obtained oleogels at a concentration > 10% nanofiber concentration in rapeseed, walnut, and flaxseed oils. All oleogels were composed of a jammed dispersion of nanofiber mat fragments that conferred the system a gel-like behavior with good thixotropic recovery. In general, oleogel rheological properties were affected by oil type and nanofiber concentration, even if all systems showed uniform plastic deformation at increasing strain amplitude. Our results show that the milling method here developed can be a useful approach for obtaining oleogels using nanofibers obtained with USES, without the need of high temperatures or fiber pretreatments.