13-7 |
Computer simulation of capacitive radio frequency (RF) dielectric heating on vegetable sprout seeds |
J. YANG, Nutritional Sciences, Univ. of Connecticut, 3624 Horsebarn Rd. Ext. U-17, Storrs, CT 06269 and Y. Zhao, Dept of Food Science & Technology, Oregon State Univ., 100 Wiegand Hall, Corvallis, OR 97331. A food safety intervention method of utilizing radio frequency (RF) dielectric heating has been suggested to eliminate pathogens in vegetable sprout seeds. Understanding the heating performance of seeds in RF system is essential for developing such microbiologically safe process. Computer simulation of RF heating can save significant time and resources due to the complexity of the process. Our objective was to explore the application of a commercial program package “TLM-FOOD Heating” to simulate the heating performance of radish and alfalfa sprout seeds packed inside rectangle seeds boxes during RF heating. TLM-FOOD HEATING software package was utilized to simulate RF heating on seeds. Temperature and moisture-dependent thermal properties, and temperature and frequency-dependent dielectric properties of seeds were integrated into the models. The electromagnetic field and heat diffusion was modeled using transmission line matrix method in time domain and standard explicit finite-difference method, respectively. Seeds placed inside polystyrene boxes were described as an infinite rectangle, where nonuniform boundary conditions were considered. The three-dimensional finite-element model was then validated using experiments conducted in a 34 MHz RF system. The time-temperature profiles of the seeds at four different locations (center, top, edge, and bottom) within the seeds box were simulated. Simulated temperature distribution agreed favorablely with experimental results. Differences between simulated and measured temperatures in the center, top, edge, and bottom were 1.8 0C, 1.1 0C, 8.9 0C, and 13.6 0C for radish seeds after 108 s heating, and were 0.9 0C, 2.4 0C, 7.75 0C, and 14.3 0C for alfalfa seeds after 80 s heating. Computer simulation can dramatically reduce the number of experiments needed to predict the location of cold points and the time-temperature history in a heating system. Generated information would allow the appropriate design of a RF system for ensuring the safe production of vegetable sprouts.
Session 13, Food Engineering: Thermal processes
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