On the clustering of triacylglycerols in the molten state

Abstract

The liquid–solid phase transition of triacylglycerols (TAGs), the main components of edible fats and oils is central to the production and sensory properties of many processed foods. While there has been extensive research on the nucleation and growth of fats, there remains a dearth of knowledge regarding the structural organization of TAGs in the liquid state. From a molecular perspective, TAGs consist of three alkyl chains esterified to a glycerol backbone. Several models based on experiment and simulation have helped to unveil TAG organization in the molten state. However, more evidence for their structural organization is necessary. Here, we provide simulation and experimental insights on the structural organization of molten tripalmitin using small-angle neutron and x-ray scattering, and wide-angle x-ray scattering. In agreement with recent work, we also propose a model in which TAGs associate as clusters via glycerol-glycerol interactions, with their alkyl chains extending outwards in a loose shell. Our model, however, highlights and demonstrates the dynamic nature of clusters, where TAGs can transfer from one cluster to another via diffusion. The average number of TAG molecules per cluster varies from 5 to 9 and decreases with increasing temperature, which results in a smaller average distance between clusters. Overall, this study strongly suggests that prior to the onset of nucleation, TAGs are associated as dynamic clusters formed via intermolecular interactions between neighboring glycerol cores.