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Title: NONDESTRUCTIVE SENSING OF BULK DENSITY AND MOISTURE CONTENT IN SHELLED PEANUTS FROM MICROWAVE PERMITTIVITY MEASUREMENTS

Author
item TRABELSI, SAMIR - UNIV OF GEORGIA
item NELSON, STUART

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2004
Publication Date: 9/19/2005
Citation: Trabelsi, S., Nelson, S.O. 2005. Nondestructive sensing of bulk density and moisture content in shelled peanuts from microwave permittivity measurements. Food Control. 17:304-311, 2006.

Interpretive Summary: Knowledge of moisture content in shelled peanuts is critical for their safe storage, quality assessment, and processing for food products. Therefore, there is a need for developing principles and improved methods for real-time sensing of moisture content in shelled peanuts. This paper describes microwave electrical methods for moisture content and bulk density (packing density) determination from measurement of the electrical characteristics of the shelled peanuts known as dielectric properties. The measurement principle is nondestructive and instantaneous. It is based on the interaction of the electric fields and shelled peanuts at microwave frequencies between 7 and 12 GHz. These dielectric methods depend on relationships between the dielectric properties of the peanuts and their physical properties such as moisture content, bulk density, and temperature. By expressing these relationships mathematically, the moisture content can be determined even though the packing density may fluctuate, and the bulk density can also be determined simultaneously from the same measurement of the dielectric properties. Analysis of experimental data has shown that moisture content can be measured by the new techniques with accuracies of one-half of one percent moisture or better. Bulk density can be measured with an accuracy of less than one percent. The techniques, with suitable development, could be incorporated in hand-held meters or on-line sensors, thus providing new tools for better management of moisture content with subsequent reductions in losses to producers and processors and improved and safer products for the consuming public.

Technical Abstract: Dielectric-based methods were used to determine nondestructively and simultaneously bulk density and moisture content in shelled peanuts from measurement of their relative complex permittivity at microwave frequencies (7 to 12 GHz) and 24 degrees C. The first method is based on direct relationships between the two components of the relative complex permittivity (dielectric constant and dielectric loss factor) and the bulk density and moisture content. The second method allows bulk density determination without knowledge of moisture content and temperature of shelled peanut samples from a complex-plane representation of the relative complex permittivity. Finally, moisture content in shelled peanuts is determined independent of bulk density changes with the use of density-independent permittivity functions. Statistical analysis provided bulk density and moisture content calibration equations at several microwave frequencies along with corresponding standard errors of calibration over wide ranges of bulk density and moisture content.