30D-2 |
Dielectric properties of salmon (Oncorhynchus keta) and sturgeon (Acipenser transmontanus) caviar at 27 MHz and 915 MHz as a function of temperature |
M. AL-HOLY1, Y. Wang2, J. Tang2, and B. A. Rasco1. (1) Department of Food Science and Human Nutrition, Washington State University, Box 646376, Pullman, WA 99164, (2) Department of Biological Systems Engineering, Washington State University, Box 646120, Pullman, WA 99164 The rapid heating rate for radiofrequency (RF) and microwave heating provides a major advantage compared to conventional thermal processing, particularly for heat sensitive high value food products. Knowing the dielectric properties of a food is necessary for designing a processing (e.g., pastuerization or sterilization) system since these parameters affect the coupling and distribution of electromagnetic radiation during the heating process. The objectives of this study were to determine the dielectric constant and loss factors for salted and unsalted salmon (0.5, 2.5% salt) and sturgeon (0.2, 4% salt) caviar at 20-80oC, 1 MHz - 1800 MHz, with an emphasis on frequencies used in industry (27 and 915 MHz). Caviar proteins denature above 80oC. An Agilent 4291 B Impedance Analyzes, an open-ended coaxial probe, and a custom built test cell were used for measurements. Sample size was ca. 15 g. Dielectric constant (e') and dielectric loss factors (e") were measured at 20-80oC and from 1 to 1800 MHz. Dielectric constant (e') and dielectric loss factor (e") for salmon and sturgeon caviar increased with increasing temperature at both 27 MHz and 915 MHz. e' and e" were higher for salted caviars as compared to unsalted products. Both e' and e" decreased as frequency increased. Penetration depths were estimated from dielectric property data. Dielectric properties of caviar are affected by temperature, frequency and salt content. Knowing how dielectric properties change as a function of these parameters will aid in the development of a dielectric heating process that can produce a safe, high quality product.
Session 30D, Food Engineering: Physical and chemical properties
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