Crystalline microstructure and physicochemical properties of olive oil oleogels formulated with monoglycerides and phytosterols

Edible oleogels are oils structured with non-triglyceride networks, that can be used as alternative solid-like fats. The formation of olive oil oleogels structured with monoglycerides (10%, 15% and 20% MGs) and 15% MGs in combination with 5% phytosterols (PS) was investigated. Effects of storage time (0–14 d) and temperature (−20 °C, 5 °C and 25 °C) on physicochemical properties of oleogels were probed by polarized light microscopy, large deformation mechanical measurements (hardness, gel strength), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The inclusion of 5% PS into a MG-olive oil based (15%) matrix enhanced the hardness and gel strength of the PS-MG composite oleogels, due to the fact that the PS prevented a high-level organization of MGs, as evidenced by reduced melting enthalpy values, compared to oleogels formulated solely with MGs. The 15% MGs - 5% PS oleogels stored at −20 °C exhibited the strongest mechanical properties throughout storage. A gradual transformation of the crystalline morphology (sub-α to β-crystals) was also observed over time, as probed by microscopy and FTIR analysis. The rate of these changes was faster at higher storage temperatures due to enhanced mobility of the MG molecules.