Verification of hybrid mixture theory based two-scale unsaturated transport processes using controlled frying experiments

Involvement of unsaturated transport and high temperatures during frying of foods makes it a challenging process to study via experiments and computer simulations. The objective of this research is to validate the hybrid mixture based unsaturated transport theory of Takhar (2014) via controlled frying experiments. A hollow Teflon disc is used to insulate the edges of potato disc to ensure that frying is controlled, one-dimensional, and oil uptake and moisture loss happen only through top and bottom surfaces. The model was used to predict moisture and oil content, evaporation rates, temperature distribution, and pore and gas pressure profiles as a function of frying time and temperature. Percentage average absolute difference (AAD) between predicted and experimental values for moisture content was 3.89%, 5.7% and 5.5% and oil content was 14%, 31% and 20% at 150, 170 and 190 °C respectively. Simulations showed that oil penetrated to only 0.5 mm into the potato disc. Removal of surface oil improved the prediction of experimental oil content. Maximum evaporation rate of 0.13 kg/m³ s was observed near the surface of potato slice at 150 s frying time resulting in rapid moisture loss. Pore pressure remained negative beyond 90 s frying time, which may act as a driving force for oil uptake.