29D-18 |
Effect of power level and cycling in near-infrared heating of foods |
M. F. ALMEIDA, Dept. of Food Science & Technology, Cornell Univ., 175 Riley-Robb Hall, Ithaca, NY 14853-5701 and A. K. Datta, Dept. of Biological & Environmental Engineering, Cornell Univ., 208 Riley-Robb Hall, Ithaca, NY 14853-5701.
Although ovens having infrared heat source have been around for a long time, comprehensive engineering understanding of the radiative exchange in the oven-food system has not been reported. Optimization of the power level, achieved through power cycling, depends on the wavelength (near, mid and far infrared) dependence of food properties, geometry of the system and other factors. To optimize, i.e., to obtain the fastest heating with the best possible quality, it is important to have a detailed quantitative analysis of the process. This study develops a radiative heat exchange model to understand how the energy flux over the food surface inside an oven depends on various process parameters such power levels and cycling, wavelength of radiation, food geometry and oven wall surface properties. A numerical computer model of radiative heat exchange of the oven-food system was developed using the commercial software FIDAP. The model is validated using the GE AdvanitumTM oven that has a novel near-infrared source. Measured temperature and heat fluxes over a slab of potato compared well with model predictions. Radiative fluxes at food surface varied from 300 - 500 W/m2 at the top surface (25.4 cm from source) to 700-1300 W/m2 at the bottom surface (2.5 cm from source). Oven walls having a higher emissivity of 0.8 compared to 0.1 decreased the radiative flux delivered to the food surface by almost half. Effect of power levels, studied through various duty cycles of the infrared power shows the heat flux at the food surface depends on the cycling parameters. The extremes of duty cycles gave food surface heating rates in the 0.6 - 2.6 ºC/s range. The results should lead to a systematic and novel improvement in the design of ovens in order to provide the desired heating patterns for a particular food in the fastest possible way.
Session 29D, Food Engineering: Thermal processes
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