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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

2007 Annual Report


1a.Objectives (from AD-416)
To identify relationships between dielectric properties of agricultural products and their important quality characteristics and to develop sound scientific principles for measuring these characteristics through interaction of radio-frequency and microwave electromagnetic fields with the products. Emphasis will be placed on development of improved technology for reliable, accurate moisture sensing in cereal grains and their products applicable to on-line measurement and monitoring of moisture content.


1b.Approach (from AD-416)
Laboratory mesurements on grain and seed samples, computation of dielectric properties, and analyses of resulting data, including suitable graphical techniques, will be performed on several kinds of grain and seed of economic importance. Variables will include kind of grain or seed, frequency used, moisture content, temperature, and bulk density of the grain or seed sample. Resulting data will be studied to determine behavior of the dielectric properties with respect to all variables, and results will be examined to verify relationships between and among the variables to determine whether or not behavior is in agreement with known principles or previous observations. The testing of density-independent calibration functions of the dielectric properties for their success in predicting moisture content of the various kinds of grain and seed, independent of bulk density, will be conducted. Data acquired at selected frequencies will be evaluated to identify advantages of certain frequency ranges for practical moisture sensing for each of the grain types being studied. In parallel with the moisture sensing, performance of measurement systems in sensing the bulk densities of the different kinds of grain and seed will also be assessed. The indicated universal character of the best density-independent calibration function for predicting moisture content of the different kinds of grain and seed will be tested on additional granular materials to determine the degree of its universal character. Desired characteristics for practical moisture sensors will be determined and prototype moisture meters will be developed and tested to demonstrate feasibility so that private industry can be interested in commercial development.


3.Progress Report
(See 4. Accomplishments)


4.Accomplishments
1. Inexpensive microwave sensor for real-time, nondestructive moisture content and bulk density determination in grain and seed. Moisture content of grain and seed is crucial information for safe handling and storage, and improvements are needed for on-line applications. A microwave sensor made with off-the-shelf components was assembled, tested and calibrated for wheat, corn, and soybeans. Five different calibration algorithms which provided bulk density and moisture content from measurement of attenuation and phase shift were implemented. The sensor was designed for easy mounting in combines, grain elevators, chutes…etc. Results on wheat, corn and soybeans are similar to those obtained with expensive and sophisticated measuring systems (vector network analyzer). This will encourage companies to license this technology and commercialize it for widespread use (we hold two patents on this technology). In turn, use of reliable and real-time density and moisture sensors will enhance the quality of grain and seed; avoid spoilage and waste; and overall augment competitiveness of American agricultural products in the global market. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a, 1b, and 1d.

2. User-friendly software for free-space transmission measurement of dielectric properties of materials. Free-space measurement of dielectric properties of materials can be tedious, particularly when investigating effects of several variables such as frequency, temperature, moisture content, and bulk density for granular and particulate materials. In addition, measurements on thick slabs of materials require correction of phase shift. Software was developed that automates the whole measurement sequence with several phase correction options. This will reduce considerably the time needed to collect and analyze the data. Also, its user-friendly interface will allow workers without any background in microwave measurement techniques to get the job done. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Area 1b.

3. Dielectric measurements on honeydew melons and watermelons. There is no reliable subjective method for nondestructively determining the quality of melons, so a nondestructive sensing technique would be of value. The dielectric properties of honey dew melons and watermelons 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. If the usefulness of this correlation can be confirmed, means could be developed for sensing quality of these melons nondestructively by high-frequency or microwave fields. Development of instruments based on these findings would be useful in sorting them for quality and providing high quality products for consumers. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a and 1b.

4. Dielectric spectroscopy of fresh chicken breast meat. Quality attributes of fresh chicken breast meat are of prime importance to producers and consumers, and rapid nondestructive techniques are needed for quality measurement. Dielectric measurements over a broad frequency range with a coaxial-type probe were used to explore existence of correlations with quality attributes associated with pale exudative condition (PSE) and water holding capacity. This nondestructive rapid method can be used for real-time assessment of quality characteristics of fresh chicken breast meat. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a, 1b, and 1c.

5. Dielectric spectroscopy of fresh beef meat. In the beef industry, tenderness of fresh meat determines the value of meat cuts. There is a growing need for real-time nondestructive determination of beef tenderness including tests on live animals. Developing sensing devices for this purpose would be of great value. Dielectric properties of fresh beef meat of different degrees of tenderness were measured in the frequency range from 200 MHz to 20 GHz at temperatures ranging from 0 oC to 70 oC. Data collected will be useful for scientists and engineers in designing methods and sensors for rapid and reliable tenderness determination. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a, 1b, and 1c.

6. Dielectric behavior of water in grain and seed. Dielectric properties of chemically bound water are not well understood. A better understanding will certainly improve design and accuracy of indirect dielectric methods for moisture sensing in granular materials. For this purpose, changes in dielectric properties of wheat, corn, and soybeans of different moisture contents were tracked as their temperature increased from -80 oC to 24 oC. This study revealed a significant change in the dielectric properties at around -20 oC which could be considered as the freezing temperature of bound water. The data collected would help scientists in modeling bound water in biological materials which in turn result in more effective methods for moisture sensing. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a, 1b, and 1c.

7. Dielectric characterization of high moisture corn hybrids. Existing electronic moisture meters fail to predict moisture accurately in granular materials of high moisture content. Measurements on high moisture corn hybrids with an in-house developed microwave moisture sensor provided moisture within an acceptable range of error from measurement of their dielectric properties. This study showed the performance of the microwave sensor prototype and the data collected would be helpful in future sensor designs. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a and 1b.

8. Transient behavior of corn samples of differing moisture contents in reaching moisture equilibrium. There is a recurrent problem in accurately sensing moisture content in granular materials with nonhomogeneous moisture distributions. Microwave dielectric properties of mixtures of two samples of corn with different moisture contents were tracked versus time. This study provided new insights into the dynamics of moisture redistribution within the grain sample. Consequently, a better reading of moisture content can be achieved when using nondestructive microwave moisture sensors which should help to alleviate the problem. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a and 1b.

9. Dielectric measurement of eggs freshness. There is a growing demand for instantaneous nondestructive determination of egg freshness during processing. Changes of dielectric properties of albumen and yolk of eggs during storage were measured in the frequency range between 10 MHz and 1800 MHz at room temperature. The data collected indicate the possibility for predicting freshness of eggs (Haugh unit and yolk index) from their dielectric properties. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a and 1b. 10. Moisture mapping in cotton bales. Existence of spots of higher moisture than desired inside a cotton bale causes fungi growth which results in spoilage and loss of cotton bales. Existing means for moisture detection inside cotton bales are inadequate and often present unacceptable errors. Feasibility of moisture mapping inside a cotton bale with a microwave moisture prototype was carried out successfully, demonstrating a potential solution to this problem. Successful development of practical instrumentation for this purpose could result in substantial savings by preventing cotton spoilage. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a, 1b, and 1c.

11. Dielectric spectroscopy of apples during storage. Apples and some other fruits can be stored for periods of time with maintenance of good quality. However, rapid nondestructive techniques for determining quality are not available and would be useful in storing apples. The dielectric properties of fresh apples were measured over ten weeks of storage and correlations with firmness, soluble solids content, and pH were studied. A high correlation was obtained between dielectric properties and soluble solids content, but the usefulness was not yet confirmed. If useful correlations can be confirmed, nondestructive techniques might be possible for measuring quality, which would be useful to producers and consumers. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a, 1b, and 1c.

12. Dielectric spectroscopy measurements for development of fitting functions for dielectric behavior of complex biological systems. Mathematical functions to describe the frequency-dependent behavior of the dielectric properties of biological systems are very difficult to obtain. With the cooperation of a theoretical physicist at Kazan State University, Tatarstan, Russian Federation, dielectric spectroscopy data for fresh fruits and vegetables, stored-grain insects, and hard red winter wheat, were fitted with 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, vegetables, and other agricultural products. 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. National Program 306 Component: Quality Characterization, Preservation, and Enhancement, Problem Areas 1a and 1b.


5.Significant Activities that Support Special Target Populations
None


6.Technology Transfer

Number of non-peer reviewed presentations and proceedings15

Review Publications
Nigmatullin, R.R., Nelson, S.O. Fractional kinetics and dielectric relaxation in complex systems:dielectric properties of fresh fruits and vegetables from 0.01 to 1.8 ghz. 2006. Signal Processing 86:2744-2759.

Nignatullin, R.R., Arbuzov, A.A., Nelson, S.O., Trabelsi, S. 2006. Dielectric relaxation in complex systems: quality sensing and dielectric properties of honeydew melons from 10 MHz to 1.8 GHz. Journal of Instrumentation (JINST) 1 P10002. pp. 1-19.

Trabelsi, S., Nelson, S.O. 2006. Microwave sensing technique for nondestructive determination of bulk density and moisture content in unshelled and shelled peanuts. Transactions of the ASABE. 49(5):1563-1568.

Nigmatullin, R.R., Nelson, S.O. 2006. New quantitative "reading" of dielectric spectra of complex biological systems. IEEE Transactions on Dielectrics and Electrical Insulation. 13(6):1325-1334.

Nelson, S.O., Trabelsi, S., Kays, S.J. 2006. Dielectric spectroscopy of honeydue melons from 10 mhz to 1.8 ghz for quality sensing. Transactions of the ASABE. 49(6):1977-1981.

Trabelsi, S., Nelson, S.O. 2007. Influence of Nonequilibrated Water on Microwave Dielectric Properties of Wheat and Related Errors In Moisture Sensing. IEEE Transactions on Instrumentation and Measurement. 56(1): 194-198.

Nelson, S.O., Guo, W., Trabelsi, S., Kays, S.J. 2007. Dielectric Spectroscopy of Watermelons for Sensing Quality. Measurement Science and Technology. Measurement Science and Technology, Vol. 18, pp. 1887-1892, 2007.

Trabelsi, S., Nelson, S.O. 2007. On the Accuracy of Bulk Density and Moisture Content Prediction in Wheat from Near-field Free-space Measurements. Review Article. Technishes Messen Vol 74, No. 5, pp. 280-289, 2007.

Guo, W., Nelson, S.O., Trabelsi, S., Kays, S.J. 2007. 10- to 1800-mhz dielectric properties of fresh apples during storage. Journal of Food Engineering.

Wen-Chuan, G., Nelson, S.O., Trabelsi, S., Kays, S.J. 2007. Dielectric Properties of Honeydew Melons and Correlation with Quality. Journal of Microwave Power and Electromagnetic Energy.

Last Modified: 9/2/2014
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