30D-3 |
Dielectric properties of shucked oysters |
X. HU, Biological Systems Engineering, Virginia Polytechnic Institute and State University, 200 Seitz Hall, Blacksburg, VA 24061 and P. Mallikarjunan, Biological Systems Engineering, 312 Seitz Hall, Blacksburg, VA 24061. Microwave processing of oysters to eliminate pathogens present while keeping their raw taste gained interest recently because it is quick and simple. In order to obtain better quality control during microwave processing, it is necessary to study the dielectric properties. However, there were almost limited data available on oysters’ dielectric properties. Thus, the main objective of this study is to measure the dielectric properties of shucked oysters in the frequency range of 300 to 3000 MHz at temperatures from 1 to 55 °C. The permitivity of shucked oysters was measured by an open-ended coaxial-line probe, connected to a network analyzer. The oyster sample was firstly placed inside a plastic bag and immersed in a constant temperature circulator until the center of the oyster reached the desired temperature. It was then placed in a stainless steel sample cup. The temperature of the sample holder was controlled by circulating ethylene glycol around it. During the dielectric properties measurement, a handheld digital thermometer was used to monitor the temperature of the sample. The dielectric constant decreased from 64.02 to 50.89 at 915 MHz and 59.10 to 47.67 at 2450 MHz respectively as temperature increased. The loss factor of oyster increased from 13.84 to 20.14 at 915 MHz, while the similar trend was not found at 2450 MHz. Regression models were developed to define the changes in the dielectric properties with temperature. Comparing the results of this study with the food map at 25oC, the penetration depth of raw oyster meat of 1.1 cm was very close to the raw meat and shrimp group with a dielectric constant of 55 and a loss factor of 14. The dielectric properties determined from this study can be used to predict suitable heating profiles for microwave processing and obtain effective pathogen reduction without sacrificing the product quality.
Session 30D, Food Engineering: Physical and chemical properties
|