3D structure of protein networks and lipid globules in heat-treated egg yolk revealed by x-ray holo-tomography

Upon heating, egg yolk transforms from a liquid to a grainy gel due to a combination of lipid aggregation, protein denaturation-aggregation-gelation and other processes. This heat-induced solidification of egg yolk can serve as a useful model system for the investigation of protein denaturation and gelation in biological systems in general. Using x-ray holographic tomography, we studied the heat-induced changes in egg yolk on the micron to sub-micron length scale. In contrast to electron microscopy, x-ray holography does not require sample staining, fixation, or drying, which potentially alter the sample and harm sample fidelity. Our results reveal a developing separation between proteins and lipids with fatty components rapidly aggregating into large globules around 40 µm in size.