Oil structuring through capillary suspensions prepared with wheat middlings micronized directly in oil by high-pressure homogenization

Abstract

Oleogels have been proposed as suitable systems for replacing unhealthy saturated fats in food preparations. This study aimed to structure sunflower oil through capillary suspensions using wheat middlings (WM), a residue of the wheat milling process, as the solid fraction with structuring properties. For the first time, high-pressure homogenization (HPH) was applied directly to WM dispersed in oil to reduce particle size, activate fibers, and release high-value intracellular compounds into sunflower oil. The optimized formulation of WM-in-oil-suspensions was then used to prepare capillary suspensions by adding water as a secondary immiscible fluid. Water addition drastically altered the rheological behavior and strength of oil suspensions due to the establishment of capillary forces and formation of a percolating particle network. The strength of capillary bridges depended on the particle size distribution and surface properties of WM particles and the fraction of added water (ranging between 5 and 80% v/v with respect to oil). The oil suspension at 30% w/w of HPH-treated WM solid fraction (80 MPa for 20 equivalent passes) with the addition of 50% v/v of water exhibited an apparent "transitional" yield stress >300 Pa, corresponding to gel-like behavior. Additionally, HPH treatment released antioxidant compounds contained in the solid matrix into the system. These results highlight that the resulting capillary suspension is a promising material for formulating healthier and more sustainable food products as an alternative to solid fats, with potential applications based on reduced overall caloric content and added health benefits related to dietary fiber.