Tuning Suspension Rheology in Hybrid Capillary Suspension-oleogels for Edible Oil Structuring

Awareness surrounding the negative health effects of saturated fat continues to result in their removal from processed foods. One of the key tools to structure oil is oleogelation, which relies on the formation of a self-assembled crystalline or fibrillar network that entraps liquid oil and results in a viscoelastic material. Yet, a significant impediment to the uptake of oleogelation by the food industry is the stability of oleogels once food dispersions such as powders are incorporated within them. Here, we propose the development and characterization of a hybrid method for structuring edible oils that relies not only on oleogelation, but also on the use of capillary suspensions. For particles suspended in an edible oil, the addition of a small amount of water can lead to the formation of capillary bridges between particles which greatly hinders particle sedimentation and results in a gelled state with solid-like properties. Our focus is on the combination of wax oleogels made with hexatriacontane and capillary suspensions consisting of surface-modified glass beads with a range of hydrophobicities. The compositions tested consist of ca. 33 wt% particles, up to 15 vol% water, up to 2 wt% wax with the remainder being canola oil. We demonstrate that surface molecular interactions play an important role in capillary network formation, morphology, wax crystallization and oleogelation. We show that particle polarity dictates the required volume of water needed to form sample-spanning capillary networks. Hydrophobic particles cause hexatriacontane to crystallize at higher temperatures without altering crystallinity. The hybrid materials possess tunable elasticity corresponding to the amount of added water, while the firmness of the material is controlled by the wax content. This study shows that by tailoring the composition of the hybrids, we can develop materials with a library of textures that range from pourable materials to self-supporting gels.