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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Quality and Safety Assessment Research Unit » Research » Publications at this Location » Publication #318897
Title: Dielectric properties for prediction of moisture content in Vidalia onions

Author
item McKeown, Murat
item Trabelsi, Samir
item TOLLNER, ERNEST W. - University Of Georgia

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 6/22/2012
Publication Date: 7/29/2012
Citation: Mckeown, M.S., Trabelsi, S., Tollner, E. 2012. Dielectric properties for prediction of moisture content in Vidalia onions. American Society of Agricultural and Biological Engineers Annual International Meeting. ASABE Paper No. 121337850.

Interpretive Summary: Dielectric properties, electrical characteristics, of agricultural products are highly correlated with the moisture content of those materials. Therefore, moisture content, an important characteristic of agricultural products, can be rapidly determined with appropriately designed electrical instruments. Microwave frequencies offer advantages in reliable measurement of moisture content in grain and other products. Thus microwave sensing provides a means for nondestructively determining the amount of moisture in materials by sensing the dielectric properties of the material. In this study, dielectric properties of Vidalia onions were analyzed for moisture dependence at a microwave frequency of 13.36 GHz at 23°C for moisture contents rangin between 6% and 92%. Dielectric properties were measured with an open-ended coaxial-line probe and a network analyzer. Linear models for the dielectric constant, dielectric loss factor, and a density-independent function of those dielectric properties were developed and evaluated for calibration effectiveness in predicting moisture content of Vidalia onions. Results showed that use of a density-independent function was more effective in prediction of moisture content than using dielectric properties alone. The measurements and models presented in this paper constitute the foundation for the development of a sensor for determining the degree of curing an onion has undergone, because curing is related to tissue moisture content. Further development of instrumentation for application in onion storage management could provide new useful information for quality control that would benefit growers, processors and the consumer.

Technical Abstract: Microwave Sensing provides a means for nondestructively determining the amount of moisture in materials by sensing the dielectric properties of the material. In this study, dielectric properties of Vidalia onions were analyzed for moisture dependence at 13.36 GHz and 23°C for moisture content between 6% and 92%. Dielectric properties were obtained using an open-ended coaxial-line probe connected to a network analyzer. Linear regression models were developed using the dielectric constant, dielectric loss factor, and a density-independent function. Models were evaluated for calibration effectiveness in predicting moisture content using coefficient of determination and standard error of calibration In order to validate the models, a standard error of performance was calculated from a set of observations that were not used in the calibration. Preliminary results showed use of a density-independent function was more effective in prediction of moisture content than using dielectric properties alone. The measurements and models presented in this paper constitute the foundation for the development of a sensor for determining the degree of curing an onion has undergone.