Unraveling the hierarchical structure of saturated monoacid triglycerides during crystallization: a comprehensive time-resolved X-ray scattering study

During the crystallization of triglycerides, TAG molecules self-assemble in distinct structures at different length scales. The overall size and morphology at the different aggregation levels strongly impact the triglyceride’s bulk macroscopic properties. So far, these morphological features have yet to be featured in the design of novel fat systems, presenting an exciting opportunity for reducing saturated fatty acids and enhancing the macroscopic properties of fat-rich products. In this presentation, we characterize the self-assembly of triglycerides during crystallization. For this, 30% dilutions of monoacid saturated triglycerides were diluted in oil. Synchrotron time-resolved X-ray scattering experiments were performed during crystallization, utilizing simultaneous WAXS, SAXS and USAXS. The broad q range (0.0018 to 39.3967 nm^-1) allowed to investigate the morphology and aggregation dynamics across different dimensions, including short spacings, longitudinal spacings, crystalline nanoplatelets, etc. The effect of cooling rate (1°C/min vs 10°C/min) and TAG purity (30% tristearin in triolein vs 30% fully hydrogenated rapeseed oil in high oleic sunflower oil) are used as examples to display how differences in formulation and processing can alter the final product. In each system transition dynamics are inherently different. A new model to quantitatively assess structural transitions of crystalline nanoplatelets in the USAXS area is proposed, improving the physical interpretation of the results. Whenever possible due to a length scale overlap, the findings are compared to ex-situ microscopic techniques, such as Cryo-SEM, PCM and PLM, which allow us to validate the accuracy and interpretation of the scattering models.The ultimate goal of this research is to provide tools to route towards engineering triglyceride network structures. On the longer run, we hope that these findings can help design fat systems from the Angstrom level upwards, as opposed to starting with bulk materials and working downwards.