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Dielectric Measurement of Agricultural Grain Moisture—Theory and Applications

Moisture content is a critical variable for the harvesting, processing, storing and marketing of cereal grains, oilseeds and legumes. Efficient and accurate determination of grain moisture content even with advanced nondestructive techniques, remains a challenge due to complex water-retaining biolog...

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Autores principales: Jones, Scott B., Sheng, Wenyi, Or, Dani
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8954665/
https://www.ncbi.nlm.nih.gov/pubmed/35336259
http://dx.doi.org/10.3390/s22062083
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author Jones, Scott B.
Sheng, Wenyi
Or, Dani
author_facet Jones, Scott B.
Sheng, Wenyi
Or, Dani
author_sort Jones, Scott B.
collection PubMed
description Moisture content is a critical variable for the harvesting, processing, storing and marketing of cereal grains, oilseeds and legumes. Efficient and accurate determination of grain moisture content even with advanced nondestructive techniques, remains a challenge due to complex water-retaining biological structures and hierarchical composition and geometry of grains that affect measurement interpretation and require specific grain-dependent calibration. We review (1) the primary factors affecting permittivity measurements used in practice for inferring moisture content in grains; (2) develop novel methods for estimating critical parameters for permittivity modeling including packing density, porosity, water binding surface area and water phase permittivity and (3) represent the permittivity of packs of grains using dielectric mixture theory as a function of moisture content applied to high moisture corn (as a model grain). Grain permittivity measurements are affected by their free and bound water contents, chemical composition, temperature, constituent shape, phase configuration and measurement frequency. A large fraction of grain water is bound exhibiting reduced permittivity compared to that of free water. The reduced mixture permittivity and attributed to hydrophilic surfaces in starches, proteins and other high surface area grain constituents. The hierarchal grain structure (i.e., kernel, starch grain, lamella, molecule) and the different constituents influence permittivity measurements due to their layering, geometry (i.e., kernel or starch grain), configuration and water-binding surface area. Dielectric mixture theory offers a physically-based approach for modeling permittivity of agricultural grains and similar granular media.
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spelling pubmed-89546652022-03-26 Dielectric Measurement of Agricultural Grain Moisture—Theory and Applications Jones, Scott B. Sheng, Wenyi Or, Dani Sensors (Basel) Review Moisture content is a critical variable for the harvesting, processing, storing and marketing of cereal grains, oilseeds and legumes. Efficient and accurate determination of grain moisture content even with advanced nondestructive techniques, remains a challenge due to complex water-retaining biological structures and hierarchical composition and geometry of grains that affect measurement interpretation and require specific grain-dependent calibration. We review (1) the primary factors affecting permittivity measurements used in practice for inferring moisture content in grains; (2) develop novel methods for estimating critical parameters for permittivity modeling including packing density, porosity, water binding surface area and water phase permittivity and (3) represent the permittivity of packs of grains using dielectric mixture theory as a function of moisture content applied to high moisture corn (as a model grain). Grain permittivity measurements are affected by their free and bound water contents, chemical composition, temperature, constituent shape, phase configuration and measurement frequency. A large fraction of grain water is bound exhibiting reduced permittivity compared to that of free water. The reduced mixture permittivity and attributed to hydrophilic surfaces in starches, proteins and other high surface area grain constituents. The hierarchal grain structure (i.e., kernel, starch grain, lamella, molecule) and the different constituents influence permittivity measurements due to their layering, geometry (i.e., kernel or starch grain), configuration and water-binding surface area. Dielectric mixture theory offers a physically-based approach for modeling permittivity of agricultural grains and similar granular media. MDPI 2022-03-08 /pmc/articles/PMC8954665/ /pubmed/35336259 http://dx.doi.org/10.3390/s22062083 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Review
Jones, Scott B.
Sheng, Wenyi
Or, Dani
Dielectric Measurement of Agricultural Grain Moisture—Theory and Applications
title Dielectric Measurement of Agricultural Grain Moisture—Theory and Applications
title_full Dielectric Measurement of Agricultural Grain Moisture—Theory and Applications
title_fullStr Dielectric Measurement of Agricultural Grain Moisture—Theory and Applications
title_full_unstemmed Dielectric Measurement of Agricultural Grain Moisture—Theory and Applications
title_short Dielectric Measurement of Agricultural Grain Moisture—Theory and Applications
title_sort dielectric measurement of agricultural grain moisture—theory and applications
topic Review
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8954665/
https://www.ncbi.nlm.nih.gov/pubmed/35336259
http://dx.doi.org/10.3390/s22062083
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