Multiscale structures in fat and fat alternatives

by Prof. Elke Scholten

Monday 19 Dec 2022, 14:30 → 15:30 Europe/Berlin

PH HS 3 (Physics Department)

The properties of numerous food products, such as butter, chocolate and ice-cream, are greatly affected by the crystallization behavior of milk fats. When fat crystallizes, triacylglycerides (TAGs) form a 3-dimensional fractal network of colloidal polycrystalline particles. These TAGs can be arranged into different sub-cell structures (polymorphs) and form lamellae of different thickness. This arrangement of multiscale structures has a great impact on the functionality and sensory properties of countless products. In this presentation, we will discuss structures formed at small length scales using x-ray diffraction (WAXD). We developed a quantitative phase analysis (QPA) method, allowing us to determine different structural polymorphs using calibration factors derived from pNMR measurements and solid fat content analysis. For different types of fat, we quantified the evolution of the polymorphic phases and produced phase transition diagrams during isothermal crystallization at different temperatures. We then linked these polymorphic structures to the structural organization of the network at different length scales using a variety of techniques: the molecular level (TAG composition by GC) and the sub-cell level (polymorphism by WAXD), to the lamellar stacking (by SAXS) and up to the morphology of their polycrystalline particles (by microscopy). This way, we were able to link temperature-dependent structural changes in the crystal network to its rheological evolution.

Although fat plays an important role in many food products, the search for fat alternatives is increasing due to health and sustainability reasons. This is often done by structuring liquid vegetable oils. Here, we will highlight some strategies to structure oil using different components. We will highlight the use of oleic acid – sodium oleate mixtures, which self-assemble into a variety of different structures depending on the mixing ratio. We have used neutron scattering (SANS and USANS) to gain insights into the structural formation at small length scales into lamellar and micellar structures. These structures were related to the crystal formation and the corresponding gel strength of the mixtures.