The price paid for corn is usually based on 15.0 or 15.5 percent moisture content. However, corn must be dried below 13 percent moisture to ensure safe storage for a year or more. In the U.S., such stored corn cannot be directly remoistened before selling it, but it can be mixed with moist new-crop corn. Accurate moisture measurement of mixtures of dry and moist corn is important to permit adjustment of blending ratios to maximize profitability, but grain moisture meters are less accurate for mixtures of wet and dry grain. This research evaluated the differences between dielectric-type moisture meter results for mixed and equilibrated corn samples at different moisture levels and different measurement frequencies. Equilibrated grain samples tended to give lower moisture results than recently mixed grain samples - especially in the 1 to 10 MHz region. These differences permitted detection of mixtures by using moisture measurements at two frequencies.
The Unified Grain Moisture Algorithm is
capable of improved accuracy and allows the combination of many grain types
into a single “unified calibration”. The purposes of this research were to
establish processes for determining unifying parameters from the chemical and
physical properties of grains. The data used in this research were obtained as
part of the United States Department of Agriculture-Grain Inspection, Packers
and Stockyards Administration's Annual Moisture Calibration Study. More than
5,000 grain samples were tested with a Hewlett-Packard 4291A Material/Impedance
Analyzer. Temperature tests were done with a Very High Frequency prototype
system at Corvinus University of Budapest. Typical chemical and physical
parameters for each of the major grain types were obtained from the literature.
Data were analyzed by multivariate chemometric methods. One of the most
important unifying parameters (Slope) and the temperature correction
coefficient were successfully modeled. The Offset and Translation unifying
parameters were not modeled successfully, but these parameters can be estimated
relatively easily through limited grain tests.
Authors:Péter Mészáros, Eszter Vozáry, and David B. Funk
Generally the drying process of fruits is followed by weight loss. The weight loss characterizes only the global moisture content of fruits and does not give information about the inner state of tissue. Electrical impedance spectroscopy of biological tissues shows ab-dispersion band that is associated with membrane structures and is sensitive to their integrity and functionality. The aim of this study was to measure the impedance spectra of apple slices during drying and to correlate impedance parameters to moisture content in the different drying periods. The electrical impedance spectra of apple slices were determined during drying by an HP 4284A Precision LCR Meter in frequency range from 30 Hz up to 1 MHz. The measured spectra were approximated by Cole-impedance elements. Parameter values for the fitted curves that characterized the state of drying tissue showed good correlation with the moisture content calculated from weight loss in the two falling-rate drying periods.