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M. V. KARWE and N. Nitin. Dept. of Food Science, Rutgers, The State Univ. of New Jersey, 65 Dudley Rd., New Brunswick, NJ 08901-8520 Jet impingement technology is used to heat or cool products because of higher rates of heat transfer. Despite its advantages of shorter processing time and better quality, there is a limited understanding of detailed transport processes, particularly, heat and mass transport, in jet impingement baking. This research is aimed at developing mathematical model of transport processes during jet impingement baking. A mathematical model based on coupled heat and mass transfer within food matrix was developed to simulate crust and crumb formation. Crust was defined as a region with temperatures above T evaporation and equilibrium water content, while crumb was defined as a region of temperatures approaching T evaporation and with diffusion controlled moisture transport. Crust and crumb regions were separated by moving evaporation front. Using numerical simulation the distributions of temperature and moisture were predicted in both crust and crumb. Numerical simulations were carried out for both 1-dimensional infinite slab and 2-d axisymmetric geometries. The effects of heating medium temperature and variation of surface heat transfer coefficient on the predicted thermal and moisture profiles, and crust formation, were also studied. The surface variation in heat transfer coefficient was obtained using numerical simulation of conjugate heat transfer. Numerically obtained moisture profiles indicated a sharp drop in moisture levels in crust domain before reaching equilibrium values, while moisture levels in crumb region showed diffusion limited drop. Effect of surface heat transfer coefficient on thermal and moisture profiles within the food matrix as well as rate of crust formation, was found to be significant, particularly after the crust was formed. Developing a quantitative predictive approach based on mathematical modeling of jet impingement baking processes will provide fundamental understanding of this technology. This understanding is critical for not only optimizing existing baking processes but also to develop hybrid-baking technologies and novel products.
Session 111, Food Engineering: Modeling heat transfer and microbial inactivation
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