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Title: Dielectric relaxation in complex systems: quality sensing and dielectric properties of honeydew melons from 10 MHz to 1.8 GHz

item Nelson, Stuart
item Trabelsi, Samir

Submitted to: Trade Journal Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2006
Publication Date: 10/11/2006
Citation: Nignatullin, R.R., Arbuzov, A.A., Nelson, S.O., Trabelsi, S. 2006. Dielectric relaxation in complex systems: quality sensing and dielectric properties of honeydew melons from 10 MHz to 1.8 GHz. Journal of Instrumentation (JINST) 1 P10002. pp. 1-19.

Interpretive Summary: Dielectric properties of materials are those electrical properties that influence the interaction of the materials with electromagnetic fields. For example, the dielectric properties of foods determine how rapidly they will be heated in a microwave oven. These properties can also be utilized with appropriate electronic instruments for sensing moisture content in grain, oilseed, and other agricultural products, because the moisture content is highly correlated with the dielectric properties of the materials. Dielectric spectroscopy is a means for measuring the dielectric properties of materials over a broad range of radio and microwave frequencies. Dielectric spectroscopy data measured on tissue samples from 38 honeydew melons over the frequency range from 10 MHz to 1.8 GHz at 25 degrees Celsius were furnished to a Russian theoretician for advanced mathematical analysis of their dielectric relaxation characteristics, which determine the dielectric properties of these materials. These analyses identified nine fitting parameters, which, when used with the mathematical relationships employed, provide excellent fitting of the curves for the dielectric properties. Further, the quantified dielectric relaxation behavior provides a new description of the dielectric relaxation processes in plant tissues. With further research, the dielectric properties fitting function may be useful in the application of dielectric spectroscopy for sensing quality factors such as maturity, which could then be used in the development of new instruments for nondestructive testing of fruit and vegetable products. Such new tools would be of value to growers, packers and processors in providing products of improved quality for consumers.

Technical Abstract: Based on new data treatment methods, it is possible to identify the fitting function for the complex permittivity e(jw) measured for a complex system representing plant tissues of honeydew melons in the frequency range from 10 MHz to 1.8 GHz at 25 degrees C. The identified fitting function contains 9 fitting parameters and well describes the plant tissue permittivity. These parameters vary for different tissues; their correlation behavior with respect to soluble solids content (SSC), tissue density, and moisture content are found by a new approach based on the statistics of the fractional moments. These correlation dependencies expressed in the form of correlation functions can be used for quality sensing of different complex systems, in particular, for ripe fruits and vegetables, where direct relationships between molecular and fitting parameters are not easy to find. These correlation functions can be used for practical purposes to construct a desired calibration curve with respect to quality factors, as for example, moisture content or degree of maturity, expressed in terms of SSC value. The discovered common "universality" in dielectric behavior of such complex materials as plant tissues opens a possibility to use dielectric spectroscopy as a nondestructive method of control in analysis of electrical behavior (measured in the form of complex permittivity or impedance) for other complex materials.