Page Banner

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

2008 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
This project relates to National Program 306 Quality and Utilization of Agricultural Products Action Plan, Component 1 Quality Characterization Preservation and Enhancement. This year, research efforts focused on building, testing, and calibrating a low-cost microwave sensor prototype for simultaneous and independent determination of bulk density and moisture content in cereal grains and oilseeds and also investigating correlations between dielectric properties and quality attributes of fresh chicken breast meat, eggs, and peanuts. Successful completion of the microwave sensor prototype led to interest by a major US agricultural machine manufacturer. A material transfer agreement was signed and plans for field test this Fall were made. For shelled and unshelled peanuts, moisture content is essential in determining optimum conditions for harvesting, drying, safe storage and marketing. Also, unshelled peanuts must be hand shelled to determine the moisture content. Research efforts focused on developing a rapid and nondestructive method and instrumentation for moisture determination in peanut kernels from dielectric measurements on pods. Consequently, two microwave sensors for peanut grading were built, calibrated and tested and will be deployed, under a material transfer agreement, at two peanut buying points by mid September 2008. Quality attributes of fresh poultry breast meat are of prime importance to producers and consumers, and rapid nondestructive sensing techniques are needed to meet requirements of the highly automated poultry industry. Dielectric measurements over a broad frequency range (from 10 MHz to 20 GHz) with a coaxial-type probe were used to explore existence of correlations with quality attributes associated with pale, soft, and exudative condition (PSE) and water holding capacity. Also, dielectric data were collected with temperature varying between -15 and 70 degree C to investigate the different binding modes of water inside the chicken meat. The data collected will be instrumental in the design of a nondestructive rapid method for assessing quality characteristics of fresh poultry meat such as water holding capacity and PSE. There is a growing demand for instantaneous nondestructive determination of egg freshness during processing. Changes of dielectric properties of albumen and yolk of eggs stored at 15 and 24 degree C, respectively, were measured in the frequency range between 10 MHz and 20 GHz at room temperature. In addition, egg freshness indicators such as Haugh unit and yolk index, and viscosity were measured. The data collected will be investigated for correlating freshness of egg indicators to their measured dielectric properties. Moisture content of solid biofuels is a determinant factor in pricing, optimum combustion conditions, and storage management. Standard oven-drying techniques are time and labor consuming. In an effort to provide an alternative method that is rapid and nondestructive, a dielectric method that was initially developed for moisture content in cereal grain and oilseed was successfully tested for pine pellets and wood chips.


4.Accomplishments
1. Low-cost microwave prototype sensor for real-time, nondestructive moisture content and bulk density determination in grain and seed. Routine measurement of moisture content of grain and seed is crucial information for safe handling and storage, and improvements are needed for real-time characterization of these materials. In a move to bring closer to commercialization our patented microwave technology (we hold two patents on this technology) for nondestructive, real-time determination of moisture content and bulk density of grain and seed, a microwave sensor made with off-the-shelf components was assembled, tested and calibrated for wheat, corn, soybeans, and peanuts (pods and kernels). User-friendly software, developed in-house, integrating five different calibration algorithms provides bulk density and moisture content from free-space measurement of attenuation and phase shift. Results on wheat, corn, soybeans, and peanuts are similar to those obtained with expensive and sophisticated measuring systems (vector network analyzer). A material transfer agreement has been signed with a major United States farm equipment company which will field-test this technology in the Fall of 2008 and they have applied for licensing one of our patents. Widespread use of this technology by American farmers will enhance the quality of grain and seed; avoid spoilage and waste; and augment overall competitiveness of American agricultural products in the global market. This accomplishment relates to National Program 306 Quality and Utilization of Agricultural Products, Component Quality Characterization, Preservation, and Enhancement, Problem Area 1a Definition and Basis for Quality, Problem Area 1b Methods to Evaluate and Predict Quality and Problem Area 1c Factors and Processes that Affect Quality.

2. Determining moisture content in peanut kernels while still in the pods. Moisture content is essential in determining optimum conditions for harvesting, drying, safe storage and marketing of peanuts. Rapid means for moisture assessment are essential in minimizing aflatoxin risk during storage with subsequent improvement of kernel quality and profitability for peanut growers. Also, unshelled peanuts must be first hand shelled to determine the kernel moisture content. A dielectric-based method for simultaneous and independent determination of bulk density and moisture content in unshelled and shelled peanuts was developed. In particular, a method for moisture determination in kernels from dielectric measurements on pods was developed with three different types of unshelled and shelled peanuts (Georgia Runner, Texas Runner, Virginia, and Valencia) with varying temperature, density and moisture conditions. Measurements were conducted in parallel with a sophisticated vector network analyzer (2 to 18 GHz) and a low-cost, in-house-developed, microwave sensor. Two portable microwave sensors were assembled, tested, and calibrated. They will be deployed, under a material transfer agreement for field-testing in September at two buying points in South Georgia. This accomplishment relates to National Program 306 Quality and Utilization of Agricultural Products, Component Quality Characterization, Preservation, and Enhancement, Problem Area 1a Definition and Basis for Quality, Problem Area 1b Methods to Evaluate and Predict Quality and Problem Area 1c Factors and Processes that Affect Quality.

3. Rapid moisture measurement of solid biofuels. Biofuels represent an attractive alternative to fossil fuels. Moisture content of solid biofuels is a determinant factor in pricing, optimum combustion conditions, and storage management. Standard oven-drying techniques are time and labor consuming and do not meet the requirements of highly automated modern industries. Therefore, there is a growing need for rapid determination of moisture content in solid biofuels and dielectric-based methods provide a viable solution. Dielectric properties of pine pellets and wood chips were measured over a broad frequency range (2 to 18 GHz) in free space at room temperature. A method which allows moisture content determination independent of bulk density changes from measurement of the dielectric properties was developed. This study constitutes the basis for the development of instrumentation for rapid and nondestructive determination of moisture content in solid biofuels. This accomplishment relates to National Program 306 Quality and Utilization of Agricultural Products, Component Quality Characterization, Preservation, and Enhancement, Problem Area 1b Methods to Evaluate and Predict Quality and Problem Area 1c Factors and Processes that Affect Quality.


5.Significant Activities that Support Special Target Populations
None.


6.Technology Transfer

Number of the New MTAs (providing only)1
Number of Non-Peer Reviewed Presentations and Proceedings4

Review Publications
Wen-Chuan, G., Nelson, S.O., Trabelsi, S., Jones, D.R. 2007. 10- to 1800-mhz dielectric spectroscopy of eggs in storage. Journal of Food Science.

Guo, W., Nelson, S.O., Trabelsi, S., Kays, S.J. 2008. Radio Frequency (RF) dielectric properties of honeydew melon and watermelon juice and correlations with sugar content. Transactions of the Chinese Society of Agricultural Engineering.

Trabelsi, S., Nelson, S.O. 2008. Microwave Moisture Sensor for Grain and Seed. Biological Engineering (ASABE) 1(2): 195-202.

Nelson, S.O. 2008. Dielectric Properties of Agricultural Products and Some Applications. Research in Agricultural Engineering.

Last Modified: 8/27/2014
Footer Content Back to Top of Page