Linseed oil-based oleogels with wax versus behenate-based glycerides: crystal polymorphism, microstructure, and gel stability

Abstract

Although oleogels are promising substitutes for saturated fats, their widespread adoption is hindered by multiple factors, among which an insufficient understanding of their crystallization behavior remains a key barrier. This work presents the first systematic analysis of the crystallization behavior in thermo-reversible linseed oil (LO)-based oleogels. The investigation combines in situ X-ray diffraction with thermal and microscopic analyses across a wide temperature range (-80 °C to 80 °C). We compared three natural waxes, sunflower wax (SFW), candelilla wax (CDW), and rice bran wax (RBW), along with two behenate-based glycerides, glyceryl behenate (GB) and fully hydrogenated high erucic acid rapeseed oil (FHR), as gelators for structuring LO. While LO itself exhibited both sub-α and β′ polymorphs, wax-based oleogels predominantly stabilized the β′ form. In contrast, oleogels with FHR or GB showed coexisting α/β′ and α/sub-α forms, respectively. Additionally, a β′ to β transformation was observed upon further heating in FHR-containing oleogels. Although most oleogels exhibited higher oil-binding capacity (OBC) at 5 °C than at 25–35 °C, the GB-containing oleogel achieved the highest OBC at 35 °C. These findings highlight the essential role of gelator polymorphism and crystal morphology in tailoring oleogel properties, guiding the rational design of functional oleogels for specific applications.