88C-19 |
Dielectric properties of starch solutions in the RF range (10 to 30 MHz) |
G. B. AWUAH1, P. Piyasena2, C. Defelice2, and H. S. Ramaswamy1. (1) Department of Food Science, McGill University, 21111 Lakeshore, Ste Anne-de-Bellevue, Montreal, QC H9X 3V9, Canada, (2) Food Research Centre, Food Research Program, Agriculture and Agric-Food Canada, 93 Stone Road West, Guelph, ON N1G 2W1, Canada Due to its high penetration power, radio frequency (RF) heating is currently being explored to achieve rapid heating of foods. The effectiveness of RF heating depends on the dielectric properties of the product. The two most important factors needed for modeling RF heating systems are the dielectric constant and the loss factor. Starches are widely used as thickening agents and carrier fluids in aseptic processing of particulate-laden products. RF heating has been recognized to be feasible for such products. However, there is lack of information on the dielectric properties of starch solutions in the literature, especially in the RF range. The objective of this study was to evaluate the dielectric properties of starch solutions as affected by temperature (20 to 80C), concentration (1 to 4% w/w), RF frequency (10 to 30 MHz), and salt (0.2 and 0.5% w/w). A precision LCR meter connected to a test cell and a personal computer was programmed to collect data at selected frequencies and temperature. The relative permittivity ranged from 53 to 308 and 65 to 92 for solutions with and without salt, respectively. The corresponding loss factors ranged from 277 to 3700 and 9 to 202, respectively. Temperature, frequency, concentration and their interactions had different levels of significance on the dielectric properties of starch solutions. Salt did enhance the relative permittivity but deviated from the general trend of decreasing relative permittivity as temperature increased. The loss factor increased with increasing temperature with high concentrations giving comparatively higher values. High loss factors were found with salt enriched samples, but at a reduced penetration depth as temperature increased. The penetration depth ranged from 0.03 to 0.13 m and 0.2 to 2.6 m for samples with and without salt respectively. Predictive models were developed for the dielectric properties. Data obtained in this study could be used for modeling the temperature distribution of starch solutions during RF heating.
Session 88C, Food Engineering: Physical and Chemical Properties
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