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Dielectric Spectroscopy Studies on Honeydew Melons

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  2007 ASAE Annual Meeting  073093.(doi:10.13031/2013.23192)
Authors:   Wen-chuan Guo, Stuart O Nelson, Samir Trabelsi, Stanley J Kays
Keywords:   Permittivity; Dielectric properties; Dielectric constant; Dielectric loss factor; Loss tangent; Honeydew melons; Soluble solids content; Moisture content

The permittivities (dielectric constants, (This equation is not available in html. Please view the pdf version.), and loss factors, (This equation is not available in html. Please view the pdf version.)) were measured at 24 °C over frequencies from 10 MHz to 1.8 GHz for the exterior surface, internal tissue (pulp), and juice of 44 honeydew melons. The total soluble solids content (SSC), and moisture content of internal tissues were also determined. Better correlations with SSC were found for internal tissue (edible pulp) and juice than for the surface permittivities. The best coefficients of determination, 0.752 and 0.784 for pulp and juice, respectively, were found between loss tangents and SSC at 1.8 GHz. Linear relationships were observed in complex-plane plots between (This equation is not available in html. Please view the pdf version.) and (This equation is not available in html. Please view the pdf version.) for surface, pulp and juice permittivities, and the best coefficients of determination, (This equation is not available in html. Please view the pdf version.)=0.953, 0.954 and 0.965, respectively, were found at 1.8 GHz also. SSC can be calculated well from measured permittivity values of pulp and juice in terms of the mathematical relationship determined. However, the SSC could not be well predicted from permittivity values of external surface measurements. A high correlation, R2=0.972, between SSC and moisture content was also noted. Penetration depths for electromagnetic fields ranged from about 100 cm for surface measurements and 15 cm for pulp and juice measurements at 10 MHz to about 2 cm at 1.8 GHz for all three kinds of measurements. Further research is needed to assess possibilities for nondestructive sensing of SSC in honeydew melons.

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