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United States Department of Agriculture

Agricultural Research Service

Related Topics


Location: Quality and Safety Assessment Research Unit

2009 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
Focused on calibrating and field-testing a low-cost prototype microwave sensor for simultaneous and independent determination of bulk density and moisture content in cereal grains and oilseeds. Successful field-testing of the microwave sensor at a peanut buying point led to overwhelming interest from peanut farmers and inspectors to adopt the microwave moisture sensing technology for peanut grading. Three microwave sensors are being deployed at different peanut buying points for measurements of this year’s crop. Successful completion and testing of the microwave sensor prototype has led to two licensing applications of the microwave sensing technology by two major U.S. agricultural machine manufacturers. One license was awarded this year. Moisture content of grain and seed is a key parameter in determining optimum conditions for harvesting, drying, safe storage and marketing. A microwave sensor, made with off-the-shelf components, was assembled, tested and calibrated for rapid and nondestructive determination of bulk density and moisture content in wheat, corn, soybeans, and peanuts (pods and kernels). Results compared favorably with those obtained with expensive and sophisticated laboratory measuring systems (vector network analyzer). A microwave sensor, field-tested at a buying point in Georgia, was used for measuring peanut kernel moisture content from dielectric measurements on pods, significantly reducing time for the grading process. The moisture sensor was successfully field tested and both farmers and inspectors are interested in adopting this technology as the next standard for moisture determination in peanuts. Hearing of the successful application with peanuts, the almond community has requested an evaluation of the microwave technology for sensing moisture content in almond kernels. Quality attributes of fresh poultry meat are important to producers and consumers. Rapid nondestructive quality-sensing techniques are needed in the highly automated poultry industry. Dielectric spectroscopy offers an opportunity to develop methods and instrumentation for instantaneous assessment of quality attributes of poultry meat. Dielectric measurements over a broad range of frequency and temperature with three different probes were performed on poultry breast meat. The data collected will be used to investigate existence of correlations with parameters often used to characterize the meat quality attributes including water holding capacity, drip loss, cook loss, pH, and color. This will be instrumental in developing methods and sensors for real-time assessment of the quality characteristics of fresh poultry meat. Olive oil adulteration has economic and health-related implications with no method for rapid detection of olive oil adulteration. Dielectric and near infrared spectroscopy, along with gas chromatography, were used to identify correlations with different adulterant blend levels using canola, peanut, and sunflower oils as the adulterants. Results will be analyzed to determine feasibility of detection of olive oil adulteration with spectroscopic techniques.

Replaced by bridging project 6612-44000-027-00D due to pending OSQR review.

1. Development of a microwave sensor for rapid in-shell kernel moisture content determination. Historically, peanut grading procedures have required the cleaning and shelling of pods before the kernel moisture content can be determined with commercially available electronic moisture meters. A microwave method for determining kernel moisture content from measurements on pods was developed and successfully tested during the fall harvest at a commercial buying point with better accuracy and up to 50% faster than conventional meters. A provisional patent on the microwave sensor and algorithm has been filed and both farmers and graders have expressed interest and willingness to adopt this novel technology for in-shell kernel moisture measurement as a new standard method.

2. Inexpensive microwave sensor for instantaneous, nondestructive bulk density and moisture content determination in grain and seed. Rapid and nondestructive measurement of moisture content of grain and seed is crucial information for determining optimum harvest time, safe handling and storage, and fair trade. A microwave sensor made with off-the-shelf components was assembled, tested and calibrated for predicting bulk density and moisture content of wheat, corn, soybeans, and peanuts. This new development in microwave sensing technology has generated interest from two major U.S. farm equipment companies that filed licensing applications for the two patents on this technology and one license has already been awarded. Routine use of this technology by American farmers will allow them to improve the quality of grain and seed, avoid spoilage and waste, and augment the overall competitiveness of American agricultural products in the global market.

3. Development of type-independent calibration for moisture sensing in peanut kernels and pods. Existing electronic moisture meters require individual calibrations for each type of peanuts which complicates the calibration procedure and sometimes results in errors in moisture readings when the wrong calibration is selected. A single type-independent calibration for moisture determination in peanut kernels and pods was developed for Georgia Runner, Texas Runner, Virginia, Spanish, and Valencia peanuts. This will significantly simplify the calibration procedure of moisture meters and provide an incentive for widespread use of these meters by peanut producers and inspectors. Use of this technology will improve the effectiveness and stability of peanut moisture meters and expedite the grading process, resulting in significant time and energy savings and improvement of the quality and profitability for peanut growers.

6.Technology Transfer

Number of the New/Active MTAs (providing only)1
Number of Invention Disclosures Submitted1
Number of Other Technology Transfer1

Review Publications
Nelson, S.O., Trabelsi, S. 2009. Influence of Water Content on RF and Microwave Dielectric Behavior of Foods. Journal of Microwave Power and Electromagnetic Energy. 43(2):13-23.

Nelson, S.O., Trabelsi, S., Kays, S.J. 2009. Dielectric Spectroscopy of Melons for Potential Quality Sensing. Transactions of the ASABE. 51(6):2209-2214.

Nelson, S.O., Trabelsi, S. 2008. Dielectric Spectroscopy Measurements on Fruit, Meat, and Grain. Transactions of the ASABE. 51(5):1829-1834.

Nelson, S.O., Guo, W., Trabelsi, S., Kays, S.J. 2007. Dielectric Spectroscopy of Watermelons for Sensing Quality. Measurement Science and Technology.

Trabelsi, S., Nelson, S.O., Lewis, M.A. 2009. Effects of "Natural" Water and "Added" Water on Microwave Dielectric Properties of Shelled Corn at Microwave Frequencies. Journal of Microwave Power and Electromagnetic Energy.

Trabelsi, S., Nelson, S.O. 2007. Investigating effect of near-field free-space permittivity measurements on accuracy of bulk density and moisture content determination in grain. Measurement Science and Technology.

Trabelsi, S., Nelson, S.O. 2007. Unified Microwave Moisture Sensing Technique for Grain and Seed. Measurement Science and Technology.

Last Modified: 8/30/2014
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