Moisture, Oil and Energy Transport During Deep-Fat Frying of Food Materials

A multiphase porous media model has been developed to predict the moisture migration, oil uptake and energy transport in a food material such as a semi-dry potato during deep-fat frying. The model predictions are validated using experimental data from the literature. Spatial moisture profiles show two distinctive regions (dry or crust region near the surface and wet region in most of the core) with a sharp interface which can be referred to as the evaporation front. Spatial temperature profiles show two distinctive regions—higher but constant temperature gradient region near the surface, and lower temperature gradient region in the core. In the crust region, vapour diffusional flux is comparable with vapour convective flux. In the more moist core region, capillary flux of liquid water is comparable to the convective flux of liquid water. Therefore, all three modes of transport—diffusional, capillarity, and pressure driven (Darcy) flow are found to be important. Sensitivity of the final product moisture and temperature to changes in oil temperature, initial moisture content of the sample, thickness of the sample, and the surface heat and mass transfer coefficients are discussed.