Cereal Chem 59:473 - 476. | VIEW
Influence of Temperature on Estimation of Protein and Moisture in Wheat by Near-Infrared Reflectance.
P. C. Williams, K. H. Norris, and W. S. Zarowski. Copyright 1982 by the American Association of Cereal Chemists, Inc.
After 35 wheat samples (25 G) were ground successively on the Cyclotec grinder (recommended for near- infrared reflectance spectroscopy [NIRS] analysis), the temperature of the ground sample rose from room temperature (approximately 22 C) to about 40 C. The influence of this rise in temperature on NIR analyses was investigated using NIRS instrumentation that was calibrated with samples at equilibrium room temperature. The instrument was calibrated with seven series of samples ranging in temperature from 45 to - 10 C. This temperature range caused serious discrepancies in the analytical results. Samples at -10 C gave readings that were 1% higher than Kjeldahl, whereas the NIRS protein readings at 45 C were 0.5% lower than the true results when both series of samples were read at room temperature calibration. Discrepancies for samples of intermediate temperature fell between these extremes. Analysis verified that these discrepancies were not caused by changes in the moisture content incurred during grinding but were strictly a function of temperature change. The phenomenon appeared to be independent of algorithm. A simple, practicable, inexpensive procedure was developed for correction of the results to ambient room temperature in grain elevators.