In recent years, oleogel has been attracting attention as an edible fat aimed at eliminating trans fatty acids and reducing saturated fatty acid content in processed fat products such as margarine and shortening. Oleogel is a semi-solid molecular aggregate formed by adding less than 10 wt% of a gelling agent to liquid oil, and research for industrial applications is actively underway. In previous studies, it was the first time worldwide that the fibrous crystals formed in the oleogel produced by adding 0.5 wt% of fully hydrogenated hard palm mid-fraction (FHHPMF), which contains a high amount of PSP (a type of triacylglycerol molecule), to canola oil, identified as single crystals, known as whisker crystals. Furthermore, it was demonstrated that oleogels composed of lipid whisker crystals exhibit high storage stability and excellent viscoelastic properties. 1) Therefore, in this study, we focused on controlling the cooling time and maintaining the temperature during oleogel preparation to investigate the mechanism of lipid whisker crystal formation.
The crystal structure of oleogel made from 99.8% pure PSP and canola oil was evaluated by dark field microscopy (DFM) and transmission electron microscopy (TEM). In addition, rheological tests were conducted on oleogels made by adding FHHPMF as a gelling agent to several liquid oils and controlling the cooling time and tempering temperature. In PSP oleogel after tempering, lipid whisker crystals elongated more when tempered at high temperatures.
Furthermore, by controlling the cooling time during the initial stage of crystallization, lipid whisker crystals of sufficient length could be obtained in a short time, and such crystals also appeared even in liquid oils with different physicochemical properties. In this presentation, we will also discuss the relationship between the control of whisker crystal formation and physical properties.