73C-26 |
Mathematical modeling of impingement drying of tortilla chips |
L. M. BRAUD, R. G. Moreira, and M. E. Castell-Perez. Agricultural Engineering, Texas A&M University, 303E Scoates Hall, College Station, TX 77843-2117 The use of impingement drying in processing corn tortillas prior to frying shows feasibility in production of a lower-fat fried chip (14% w.b. vs. 23-30% for commercial tortilla chips). The need for a mathematical model of this process exists to facilitate efficient process design and optimization. Our objective was to develop a mathematical model to describe the heat and mass transfer mechanisms during impingement drying of corn tortillas. Modeling was accomplished by (1) defining the governing equations that describe the transport of heat and mass (moisture) during the drying process; (2) identifying varying boundary conditions imposed by different drying media (e.g.,air and superheated steam); (3) developing a computer algorithm that incorporated the governing equations and boundary conditions to simulate the drying process; and (4) validating the developed mathematical model with existing experimental data. Mass transfer within the product was modeled as diffusion-driven mass flux. Heat transfer was driven according to Fourier's Law of conduction. Convective heat transfer accounted for heat flow into the product at the surface. When drying in air, convective mass transfer prevailed; in superheated steam, differences in vapor pressure between the drying medium and the product surface accounted for mass transfer. Temperature and moisture content predictions followed the experimental trends with both air and steam drying (115 to 145ºC). Steam condensation unaccounted for by the model resulted in under predictions in the moisture content in steam drying at low temperatures. Product thickness and drying medium temperature had a significant effect on moisture content and temperature profile over time. The model was able to predict the trend in the temperature changes over time at the experimental conditions. This supports the validity of the governing equations for energy transfer within the product during drying and supports the usefulness of such a model as a simulation tool.
Session 73C, Food Engineering: Transport Processes and Kinetics
|