The fusion of lipid droplets is involved in fat loss during cooking of duck “foie gras”

Fat loss during cooking of duck “foie gras” is the main quality issue in processing plants. To better understand this phenomenon, a histological and ultrastructural study was conducted. The aim was to characterize changes in lipid droplets of duck “foie gras” related to fat loss during cooking. Ten fatty livers were sampled before and after cooking and prepared for optical and transmission electron microscopy. In raw livers, the lipid droplets were nearly spherical while after cooking, they were larger and lost their spherical shape. We also observed a decrease in the number of droplets after cooking, probably due to droplet fusion caused by the heat treatment. Before cooking, there were fewer lipid droplets and a higher osmium tetroxyde staining intensity in the fatty liver, which later gave a lower technological yield. Fat loss during cooking was higher when there was more fusion of lipid droplets before cooking.

Research Highlights► Microscopy methods revealed morphological changes in lipid droplets of 'foie gras' according to fat loss during cooking. ► Before cooking, the lipid droplets were small and nearly spherical. ► After cooking, the lipid droplets were larger and lost their spherical shape. ► Fat loss during cooking of duck 'foie gras' was higher when there were more fusions of lipid droplets in the raw livers.