Deep dive into the differences in crystallization and gelling behavior of sunflower wax and rice bran wax

Both waxes (SFX, RBX) have high wax ester content (0.96, 0,94 %) and similar carbon number profiles. Yet, very different gelling performance. Available data show similar WE chain lengths with the median length of RBX slightly higher. This suggests RBX as good a gelator as SFX. Despite this RBX actually results in oleogels which much lower hardness values (about a factor 7). In this contribution the effort to identify the root cause for this difference is discussed. To this end gels with standard manufacturing processes – dissolution, cooling, crystallization under quiescent conditions – were produced. All gels contained 90% of MCT oil. The 10% structurant fraction was varied to map effects of changes in composition. This exercise involved optical microscopy, hardness assessment and DSC. Different from earlier works the crystallization process was monitored continuously. Studying mixtures of RBX and SFX reveal a conversion in behavior at 40% RBX inclusion. The compact arrangements typical for RBW results in apparently unstructured areas. Free fatty acids and sterols are also present in the waxes. Consequently, these components were deliberately added to the structuring system in order to manipulate the respective crystallization behavior. Some fibre-like structures accumulating solid material have been found in RBX based gels. Additionally, the waxes have been purified by different means to strip off different minor components. Currently the mechanism behind the differences could not be identified unambiguously. However, the addition of behenic acid at high levels induced in combination with RBX a structure similar to SFX. Significant changes occurred after purification. In particular the monitoring of the process illustrates that the crystallization happens stepwise. It will be discussed if this is driven by either coexisting mixed crystal formation or polymorphism.