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Calibration and Field Standardization of Foss Grainspec Analyzers for Corn and Soybeans

Connie L. Hardy, Glen R. Rippke,
Charles R. Hurburgh, Jr. and Thomas J. Brumm

United States grain handling and trade has traditionally been done on a commodity basis. Most grain quality tests under the present grain standards are measures of physical condition. Though these tests serve as basis for trading of generic commodity grain, their relationship to end-use value is hard to identify. Near infrared (NIR) technology has introduced a fast and economical method of measuring intrinsic qualities important to both processor and consumer.

The use of near infrared spectroscopy for measurement of moisture content in grain and seeds was introduced by Norris and Hart.1 It is now used to measure a wide variety of composition characteristics in biological materials. Near infrared reflectance technology allowed food processors and feed analysts to determine the nutritional composition of ground samples in a few minutes. Though economical and useful for quality control and processing, NIR has not been widely accepted by grain handlers because of the time and labor required for grinding and sample preparation.

Successful segregation of grains for intrinsic qualities depends on the ability of grain handlers to identify characteristics important end-user. Because intrinsic quality variation in a given geographic location is caused mainly by varietal and agronomic factors, the maximum differentiation exists as farmers deliver to country elevators. The economic importance of composition has been shown for both corn2 and soybeans.3 Because soybean protein and oil contents have a large impact on the amount of products derived from solvent extraction, the Federal Grain Inspection Service (FGIS) introduced soybean oil and protein (basis 13% moisture) as official criteria on September 4, 1989.4 Country elevators have recently attempted segregation of high-value soybeans3 and genetically modified corn.5

Recent developments in both near infrared reflectance and transmittance analyzers have created the ability to analyze whole grain samples for moisture, crude protein, starch, fiber and oil content in less than one minute in an elevator setting. Measurement of additional constituents may also be possible. Whole-grain near infrared technology is widely used for similar measurements in worldwide trade of wheat and other small grains. Corn and soybeans are more difficult to analyze because of their irregular shape, larger size, and range of color variation.

Although near infrared analyzers are manufactured to rigorous specifications, no two instruments have exactly the same spectral characteristics, nor can they use the same calibration without being adjusted (standardized) for each grain being tested. The issue of uniformity in testing is a major concern of grain handlers. Consistency in trade is often more critical than absolute accuracy.

This study developed a calibration and calibration transfer (for standardization) protocol for Foss Grainspec (Foss Food Technology, Eden Prairie, MN) to predict moisture, protein, oil, starch, and density in whole corn and moisture, protein, oil and fiber in whole soybeans.