High-speed computed tomography to visualise the 3D microstructural dynamics of oil uptake in deep-fried foods

Oil serves as both the high-temperature heating medium during deep-frying unit operations and a contributor to the organoleptic properties of deep-fried foods. Its absorption is linked to structural deformations during deep-frying that create pathways for oil to enter the food microstructure. This study proposes a 4D imaging system (three spatial dimensions and time) using fast synchrotron radiation tomography for in-situ visualisation during deep-frying and post-frying cooling to understand the mechanisms behind oil absorption. Using wheat flour dough as a model food system, we investigate the impact of frying oil temperature on structural deformation and pore formation in the crust and core, pore structure integrity, and oil uptake and distribution. The results show that higher temperatures lead to the formation of a distinguished crust with surface openings, facilitating greater oil absorption in small crust pores through capillary action. Comparing 3D microstructures attained at different frying oil temperatures, final oil content reaches 14.4% at 180 °C, 12.2% at 150 °C, and 1.3% at 120 °C, with temperature-dependent structural changes in pore connectivity and network integrity significantly impacting the rate of oil uptake and its distribution. Deep-frying produces foods with a porous texture, but this also raises concerns about the final oil content. Here, the authors study the pore formation of dough during rapid heating and show how oil uptake depends on the porous structure created.