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United States Department of Agriculture

Agricultural Research Service

Related Topics

Research Project: SENSING MOISTURE CONTENT AND QUALITY OF GRAIN AND OTHER AGRICULTURAL PRODUCTS BY DIELECTRIC PROPERTIES

Location: Quality and Safety Assessment Research Unit

2006 Annual Report


1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter?
Rapid means of sensing product quality, such as moisture content in cereal grains, is needed for real-time on-line monitoring of quality characteristics. Techniques for instantaneous sensing and measurement of moisture content in wheat, corn, and other cereal grains, and soybeans, peanuts, and other oilseed crops are being developed for reliable moisture measurement for on-line applications by using the dielectric properties of the products, which can be sensed with appropriate electronic instruments and which are highly correlated with moisture content. These techniques will provide reliable moisture content information that is essential for yield monitoring on harvesting equipment when combined with global positioning systems for precision farming operations and in preserving the quality of cereal grains, their products, and other agricultural products during transfer for storage and during processing. Moisture content is the single most important quality characteristic that determines the safe storage potential for cereal grains and oilseeds. Grain that is too high in moisture content is subject to attack by grain storage fungi and stored-grain insects. These infections and infestations produce spoilage and loss of value that reach significant proportions every year. Fungi produce toxins such as aflatoxins and fumonisins that are serious health hazards to man and animals that use these products for food and feed. Therefore, better information on the moisture levels of products such as cereal grains can be of significant value in maintaining quality and preventing losses and contamination. In addition, the moisture monitoring techniques will provide for better control of processing for value added applications and improved end-product quality. They will provide more precise moisture information that can be used in optimizing grain drying with resulting higher quality products and significant energy savings in grain drying operations. Reliable on-line moisture monitoring will also fill important needs in highly automated operations in agriculture, such as precision farming, yield monitoring, and in other industries as well, where real-time moisture content information is essential to efficient operations. Accurate and reliable monitoring of moisture content is also essential for fairness in trading of grain and oilseeds, for efficiency in processing, and in providing healthful food products to the consuming public.


2.List by year the currently approved milestones (indicators of research progress)
12-Month Milestones Microwave dielectric properties of wheat, corn, oats, soybeans, sunflower, safflower and canola measured as functions of frequency moisture content, temperature, and bulk density. Testing of initial patch antennas completed and required design selected. Procurement of components initiated for assembling time-domain spectroscopy (TDS) system. Dielectric properties measured for several fruits and vegetables over broad frequency range. 36-Month Milestones Preferred frequency ranges established for reliable sensing of moisture content in static samples of major grain and oilseed crops. Degree of calibration-function universality established for major grain and oilseed crops. Improved patch antennas integrated with microwave circuits needed for moisture meter evaluation. Papers presented and submitted for publication. Completion of TDS system assembly and software development initiated for dielectric properties measurements Additional products identified and evaluated for potential quality sensing studies. 60-Month Milestones Calibration equations developed as a universal density-independent moisture predictor or for classes of grain and seed crops. Performance on flowing grain samples evaluated and recommendations formulated for technology transfer. Published papers and new paper submitted. Working prototype microwave moisture meter evaluated for performance on static grain and seed samples and recommendations formulated for technology transfer. Working TDS system with broadband dielectric properties data on several agricultural products. Paper presentations and papers submitted for publication.


4a.List the single most significant research accomplishment during FY 2006.
National Program Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a, 1b, and 1c Title: Development of a prototype microwave moisture and density meter for grain and seed. We demonstrated that a single-frequency microwave meter for sensing moisture content and bulk density of grain and seed could be assembled from off-the-shelf components at relatively low cost compared to laboratory instruments used in the research. More reliable moisture and density monitoring in grain and seed is important in modern agriculture. Dielectric properties measured with the prototype meter, and calculated moisture contents and bulk densities of corn, wheat and soybeans agreed well with values determined with a sophisticated network analyzer and expensive horn/lens antennas. Software developed for use with the laboratory instrument system was also adapted to provide user-friendly operation of the prototype meter. Practical use of such instruments would provide more reliable moisture content information on combine harvesters and other grain and seed moisture and density monitoring applications to provide better information for sound management of such crops.


4b.List other significant research accomplishment(s), if any.
National Program Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a, 1b, and 1c 1. Confirmed and refined principles for microwave sensing of grain and oilseed moisture content. With new measurements and analysis of microwave dielectric properties of grain and oilseeds, we have demonstrated that a single calibration can be obtained for corn, wheat, grain sorghum, barley, and soybeans. This is important, because there is a large cost to moisture meter manufacturers in maintaining separate calibrations for all of the different kinds of grain and seed at the lower frequencies used in currently available commercial meters. At microwave frequencies, moisture content is also provided independent of the density of the grain, so that reliable moisture sensing in moving grain can be achieved. The microwave frequencies are also not affected by variations in ionic conductivity, which is responsible for errors in moisture measurement at lower frequencies. These findings will help provide the stimulus that is needed to encourage development of practical microwave moisture meters for monitoring grain and seed moisture content to assist in preserving such crops, maintaining high quality, and improving yield monitoring in precision agriculture.

2. Microwave sensing of bulk density in granular materials. The same measurement of microwave dielectric properties of grain and oilseeds that permits moisture content sensing can also be used to determine the bulk density, or packing density of the grain and seed. This provides a new technique for monitoring bulk density in granular materials, which can be useful in monitoring mass flow for grain and other materials. Bulk densities of corn, wheat, oats, barley, grain sorghum, and soybeans and peanuts were determined from measurements of microwave dielectric properties with sufficient accuracies for practical use. While the application of this finding has not been fully explored, it may eventually be useful in the monitoring of mass flow for granular materials in precision farming and other applications. Bulk density is not currently a factor in peanut grading, but might be helpful if such a rapid technique were available.

3. Dielectric behavior of water in grain and seed. New understanding of the dielectric behavior of bound water in grain and seed was achieved. This is important because the dielectric behavior of grain, which is used in sensing moisture content, is dominated by the dielectric behavior of bound water. At normal moisture contents, the water in grain is chemically bound to other molecules in the kernels. By conditioning wheat and soybeans at very low temperatures and tracking the dielectric properties as they warmed to room temperature, a freezing temperature for bound water in grain and seed was revealed. And by moistening wheat and tracking the dielectric properties as the added water diffused into the kernels, it was revealed that the dielectric properties reached equilibrium conditions within two to four hours. Furthering the understanding of the behavior of bound water in grain and seed permits the improvement of moisture sensing in these granular materials.

4. Dielectric spectroscopy of honeydew melons. The dielectric properties of honey dew melons over a range of ripeness were measured in the frequency range from 10 to 1,800 MHz and a high correlation was found with quality or sweetness as determined by optical measurements of soluble solids content. There is no reliable subjective method for determining honeydew melon quality, so a nondestructive sensing technique would be of value. If some means could be developed for sensing quality of these melons nondestructively by high-frequency or microwave fields, instruments could be designed for this purpose, which would be useful in sorting them for quality.

5. New fitting procedure for dielectric spectroscopy data. With the cooperation of a theoretical physicist at Kazan State University, Tatarstan, Russian Federation, dielectric spectroscopy data for several fresh fruits and vegetable and for four stored-grain insect species, were fitted with seven parameters which can be used to express the dielectric properties of these biological materials as a function of frequency and temperature. This accomplishment has scientific significance, because it provides an excellent fitting of the data for potential use in practical applications such as the detection of quality characteristics in fruits and vegetables. The analysis was based on known behavior of dielectric properties of matter and advanced mathematical techniques for developing the fitting parameters. The work must be considered exploratory, and the technique must be applied to new dielectric spectroscopy data taken for the purpose of distinguishing important characteristics in products for evaluation.

C. Significant Accomplishments/Activities that Support Special Target Populations None.

D. Progress Report (6612-44000-0024-01S) This report serves to document research conducted under a specific cooperative agreement between ARS and The University of Georgia. Additional details of the research can be found in the report for the parent project 6612-44000-024-00D. Methods for rapidly and reliably sensing product quality, such as grain moisture content, are needed for on-line monitoring of quality characteristics. Techniques based on measurement of the microwave dielectric properties of corn, wheat, oats, barley, grain sorghum, soybeans, and peanuts provided moisture content independent of the material bulk density, and the techniques also can provide bulk density of the grain or seed independent of moisture content. Promising results were obtained with a single moisture calibration equation for corn, wheat, barley, grain sorghum, and soybeans. A universal moisture calibration for grain would provide a significant advantage, thus, providing an incentive for development of practical microwave grain moisture sensors. Toward this end, we demonstrated that inexpensive patch antennas can be used in place of expensive microwave horn/lens antennas for reliable measurement of grain and oilseed dielectric properties and consequent determination of moisture content. A prototype microwave grain moisture meter was assembled from such patch antennas and other off-the-shelf microwave components which gave measurements in good agreement with the expensive laboratory measurement equipment. In addition, progress was made in understanding of the dielectric behavior of bound water in grain. This is important because the dielectric behavior of grain, which is used in sensing moisture content and bulk density, is dominated by the behavior of bound water.


5.Describe the major accomplishments to date and their predicted or actual impact.
National Program Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a, 1b, and 1c. Microwave measurement techniques have been developed for 2- to 18-GHz dielectric properties measurements on grain and oilseed with a microwave network analyzer, which are especially well suited for on-line measurements to determine moisture content through use of the dielectric properties. Techniques have been developed for reliable moisture sensing in grain independent of bulk density (grain packing). At microwave frequencies, measurements on wheat, corn, oats, barley, grain sorghum, soybeans, and peanuts over wide ranges of frequency, moisture content and bulk density have provided reliable moisture determination. Advanced techniques have been explored for obtaining the best calibrations for sensing grain moisture content. The new techniques for grain moisture sensing should result in development of improved moisture monitoring instrumentation that can be applied for more accurate and reliable yield monitoring on combine harvesters for precision farming and in many grain processing and product drying applications. These findings are of interest to manufacturers of moisture meters and harvesting machines. Over the past year, efforts were concentrated on developing the foundation for reliable moisture sensing in grains and oilseeds by microwave measurements and exploiting the substantial advantages that microwave frequencies offer for this application. Good progress has been made in developing density-independent moisture calibrations that promise universal applicability for grain and oilseed and in identifying cost reductions for eventual production of economically feasible practical instruments. Good progress has also been achieved on the development of a prototype microwave grain and seed moisture meter, assembled from available commercial components at much lower cost than laboratory-type equipment. New software has also been developed for efficient use of laboratory equipment and has been adapted for user-friendly operation of the prototype microwave moisture meter. Limited measurements on fruit and vegetable tissues have provided an initial database on the dielectric properties of several fruits and vegetables and revealed their frequency- and temperature-dependent characteristics. They include a frequency between 10 and 120 MHz where the dielectric constant does not depend at all on temperature and a linear model for the dielectric loss factor of nine fruits and vegetables over the frequency range from 10 to 300 MHz. These provide a background for future research on quality sensing in fruits and vegetables by radio-frequency and microwave electric fields.


6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products?
A major manufacturer of farm equipment has a new grain moisture sensor in production on its grain combines, which uses principles developed by ARS research. Consultation was provided by ARS engineers to the designers and developers of this new moisture sensor. Principles outlined in United States Patent No. 6,691,563, “Universal dielectric calibration method and apparatus for moisture content determination in particulate and granular materials,” Samir Trabelsi, Stuart O. Nelson and Andrzej W. Kraszewski.,issued February 17, 2004, have been incorporated into microwave moisture sensing equipment supplied by an instrument manufacturer in Iceland. Many reprints of published papers have been distributed in response to inquiries from all over the world. Most of these inquiries are from scientists, engineers, and graduate and undergraduate students interested in moisture sensing, microwave processing, applications of RF and microwave energy for insect control or seed treatment, and basic dielectric properties of materials and their measurement. Informal consultation was provided to representatives of a major agricultural instrument manufacturer relative to possible development of microwave grain moisture meters. Informal consultation was also provided to two foreign companies, one manufacturing industrial microwave moisture sensing equipment and another interested in sensing quality of fruits and vegetables. Research papers and consultation have been provided for companies interested in developing high-frequency and microwave equipment for nonchemical stored-grain insect control purposes in The United States, the United Kingdom, and the Ukraine. Constraints for the moisture sensing applications consist mainly of costs of developing suitable practical equipment, ascertaining reliability of the measurements, and unknown market potential for the equipment. Constraints for the insect control application are economic, including both costs of equipment for large-scale treatment and costs of operation when less expensive chemical controls are available.


Review Publications
Nelson, S.O. 2005. Useful relationships between dielectric properties and bulk density of granular and powdered materials. Proceedings of the 4th World Congress on Microwave and Radio Frequency Applications. R. L. Schultz and D. C. Folz, Editors. Arnold, MD: The Microwave Working Group, Ltd., pp. 407-416.

Nelson, S.O. 2005. Density-permittivity relationships for powdered and granular materials. IEEE Transactions on Instrumentation and Measurement. 54(5):2003-2040

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.

Nelson, S.O., Trabelsi, S., Kays, S.J. 2006. Dielectric spectroscopy of honeydew melons [Abstract] [CD-ROM]. Annual Meeting Abstracts of the American Association for the Advancement of Science, p. A146.

Trabelsi, S., Nelson, S.O. 2006. Near-field measurements of dielectric properties of granular materials with microstrip antennas for microwave-sensing applications. Research in Nondestructive Evaluation. 17(1).

Nelson, S.O. 2006. Dielectric spectroscopy of fresh fruit and vegetable tissues from 10 to 1800 mhz. Journal of Microwave Power and Electromagnetic Energy 2005. 40(1):31-47

Nelson, S.O. 2006. Dielectric properties of materials and related agricultural applications [abstract]. National Academy of Engineering Regional Meeting (June 15-16, 2006). pg 6.

Trabelsi, S., Nelson, S.O. 2006. Temperature-dependent behavior of dielectric properties of bound wataer in grain at microwave frequencies. Measurement Science and Technology. 17:2289-2293.

Nelson, S.O., Trabelsi, S. 2006. Dielectric spectroscopy of wheat from 10 mhz to 1.8 ghz. Measurement Science and Technology. 17:2294-2298.

Nelson, S.O., Trabelsi, S. 2006. Dielectric spectroscopy of hard red winter wheat. American Society of Agricultural and Biological Engineers Paper Series. Paper no. 063045.

Trabelsi, S., Nelson, S.O. 2006. Unified algorithm for microwave sensing of moisture in grain and seed. American Society of Agricultural and Biological Engineers Paper Series. Paper number 063094.

Trabelsi, S., Nelson, S.O. 2006. Temperature-dependent behavior of microwave dielectric properties of bound water in grain and seed. American Society of Agricultural and Biological Engineers Paper Series. Paper Number 066077.

Nelson, S.O., Trabelsi, S., Kays, S.J. 2006. Correlating honeydew melon quality with dielectric properties. American Society of Aagricultural and Biological Engineers Paper Series. Paper No. 066122

Trabelsi, S., Nelson, S. O. 2006. Microwave dielectric properties of grain in nonequilibrium state: effect of moisture and temperature [abstract][CD-ROM]. IEEE AP-S Symposium and USNC/URSI and AMEREM Meetings. p. 361.

Trabelsi, S., Nelson, S.O. 2006. Microwave sensing method for simultaneous and independent determination of bulk density and moisture content of shelled peanuts [CD-ROM]. IEEE AP-S Symposium and USNC/URSI and AMEREM Meetings. CD. pp. 3187-3190.

Nelson, S.O., Trabelsi, S., Kays, S.J. 2006. Corelating dielectric properties of melons with quality. 2006 IEEE AP-S Symposium and USNC/URSI and AMEREM Meetings CD. pp 4849-4852.

Nelson, S.O. 2004. Dielectric spectroscopy applications in agriculture. Final Program and Book of Abstracts, Delft University of Technology. p. 260.

Trabelsi, S., Nelson, S.O. 2006. Nondestructive sensing of granular material of physical properties by microwave permittivity measurement. IEEE Transactions on Instrumentation and Measurement 55(3):953-963..

Nelson, S.O., Trabelsi, S., Kays, S.J. 2006. Dielectric spectroscopy of honeydew melons for quality sensing. In Proceeding of the 23rd IEEE Instrumentation & Measurement Technology Conference, May 24-27,2006, Sorrento, Italy. pp. 180-182,CD.

Trabelsi, S., Nelson, S.O. 2006. Nondestructive moisture sensing in peanut kernels from microwave permittivity measurements on unshelled pods. Proceedings of the 23rd IEEE Instrumentation and Measurement Technology Conference Record, May 24-27, 2006, Sorrento, Italy. pp. 305-307,CD.

Nelson, S.O., Trabelsi, S., Kays, S.J. 2006. Dielectric properties of honeydew melons for sensing quality. Proceedings of the 40th Annual Microwave Power Symposium Proceedings, August 9-11, Boston, MA. pp. 76-78.

Trabelsi, S., Nelson, S.O., Ramahi, O. 2006. A low-cost microwave moisture sensor. Proceedings of the 36th European Microwave Conference, Manchester, UK. September 10-15,2006, pp. 447-450.

Nelson, S.O., Trabelsi, S. 2006. 10-mhz to 1.8 ghz dielectric spectroscopy of honeydew melons[abstract],September 4-7, Poznan, Poland. pp.250-251.

Nelson, S.O., Trabelsi, S. 2006. Dielectric spectroscopy studies on hard red winter wheat[abstract], September 4-7, Poznan,Poland. 4th International Dielectric Society and 9th International Conference on Dielectric and Related Phenommona. pp. 252-253.

Trabelsi, S., Nelson, S.O. 2006. Dielectric study of binding modes of water in grain and seed at low temperatures. 40th Annual Microwave Symposium Proceedings. August 9-11, 2006, Boston, MA. pp.89-92.

Kandala, C., Butts, C.L., Nelson, S.O. 2006. PARALLEL-PLATE SENSORS FOR MEASUREMENT OF MOISTURE CONTENT IN IN-SHELL PEANUTS NON-DESTRUCTIVELY. Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE). Paper number 066041.

Nelson, S.O. 2006. Agricultural Applications of Dielectric Measurements. IEEE Transactions on Dielectrics and Electricl Insulation. Volume 13(4):Page No. 688-702.

Last Modified: 4/24/2014
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