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Title: Sensing Quality of Watermelons Through Dielectric Permittivity

item Nelson, Stuart
item Trabelsi, Samir

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 3/20/2007
Publication Date: 6/10/2007
Citation: Nelson, S.O., Wen-Chuan, G., Trabelsi, S., Kays, S.J. 2007. Sensing Quality of Watermelons Through Dielectric Permittivity. Meeting Abstract.

Interpretive Summary: Interpretive Summary Sensing Quality of Watermelons through Dielectric Permittivity Techniques for nondestructive determination of quality of agricultural products are helpful to producers, handlers and processors, those marketing the produce, and consumers. Visible and physical characteristics of many fresh fruits and vegetables are available for correlation with quality, and some of these, such as color, size, weight, density, elasticity, and firmness are used in automatic sorting of some produce into different categories for the market. Electrical characteristics of fruit tissue known as dielectric properties can be sensed with electric fields for possible detection of fruit quality. Therefore, four miniature watermelons were grown and harvested with a range of maturities for dielectric spectroscopy measurements of the melon tissue to learn whether there might be differences in the dielectric properties that could be correlated with quality. The best criterion for quality is the content of soluble solids, which are mostly sugars and therefore a measure of sweetness. This requires the extraction of tissue samples from the melons and measurement of expressed juice with a refractometer instrument, which has been calibrated to indicate percentage of soluble solids. The dielectric properties of the watermelon tissues were measured over the frequency range from 10 MHz to 1.8 GHz along with refractometer determinations of soluble solids content (SSC). A high correlation was found between SSC and the dielectric properties as expressed in a complex-plane plot of the dielectric constant and loss factor, each divided by SSC. Through this mathematical relationship, SSC was calculated from measured dielectric properties, but predictions were not as high as desired, and further research is needed to assess the dielectric technique for sensing watermelon quality. The challenge in using this new principle for practical nondestructive sensing of honeydew melon quality is considerable, but development of such a melon quality meter would be helpful to melon growers and handlers in the marketing of high quality produce for American consumers.

Technical Abstract: