AN IMPROVED, EASILY IMPLEMENTABLE, POROUS MEDIA BASED MODEL FOR DEEP-FAT FRYING. Part II: Results, Validation and Sensitivity Analysis A. Halder, A. Dhall and A. K. Datta  Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY, USA. Abstract: The multiphase porous media model, developed in the companion paper, has been applied to frying of a restructured potato slice to obtain temperature, pressure, moisture, oil con- tent, acrylamide content and evaporation rate profiles, providing valuable insight into the frying process. The model is validated by comparing temperature, moisture content and crust thickness profiles from literature experimental results. A novel non-equilibrium formulation, different from the existing food literature, is able to describe well the evaporation process. Post-frying cooling is included through appropriate changes in boundary conditions. It is seen that the oil pickup mostly takes place during post-frying cooling and is due to capillary suction created by the nega- tive pressures from condensation of water –vapour. Acrylamide is formed primarily in the crust region where temperature exceeds 1008C. Sensitivity analyses of the process to surface mass transfer coefficient, evaporation rate constant and oil diffusivity show that they all have sig- nificant effects on the process. Development of this mechanistic model that is also more easily implementable than previous models should make computer-aided design and optimization of frying processes closer to reality. Keywords: non-equilibrium; potato; crust formation; oil pickup; acrylamide. INTRODUCTION Design and optimization of a frying process can greatly benefit from mathematical model of the process that provides in-depth under- standing of the physics, as was noted in the companion paper. The multiphase porous media based model developed in the compa- nion paper can provide spatial and transient temperature, pressure, water and oil satur- ation, and evaporation rate profiles. Transient and spatially varying evaporation rate, for example, has not been available in the past and can provide significant insight into the process. Many of the literature models treat evaporation at a sharp boundary and it would be useful to contrast the sharp bound- ary model with the distributed evaporation model in this study. Finally, a complex phy- sics-based model such as this one has many input parameters not all of which have been measured or readily available. A math- ematical model is very effective in under- standing the sensitivity of model predictions to the various input parameters. This serves dual purpose—it provides insight into which parameters are critical and need to be manipulated in a design process; it also guides further research by isolating the most significant parameters for which more accu- rate data may be necessary. The objectives of this research are as follows: (1) to numeri- cally solve the multiphase porous media based frying model developed in the compa- nion paper and obtain quantities such as temperature, pressure and evaporation rate; (2) to relate these quantities to quality par- ameters, i.e., crust thickness, moisture con- tent, oil pickup and acrylamide formation; (3) to determine the sensitivity of the model to various input parameters. RESULTS AND DISCUSSION Predicted temperature, moisture, pres- sure and evaporation rate are computed as functions of position and time. Distributed evaporation model used in this paper is con- trasted with sharp evaporation front model from literature. Quality parameters of crust 220 Vol 85 (C3) 220–230  Correspondence to: Professor A.K. Datta, Department of Biological and Environmental Engineering, Cornell University, 208 Riley Robb Hall, Ithaca, NY 14853, USA. E-mail: akd1@cornell.edu DOI: 10.1205/fbp07034 0960–3085/07/ $30.00 þ 0.00 Food and Bioproducts Processing Trans IChemE, Part C, September 2007 # 2007 Institution of Chemical Engineers