Measurement of transient moisture profiles and structural changes during the drying and cooling of maize using MRI
Song, Huaipu
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https://hdl.handle.net/2142/23238
Description
Title
Measurement of transient moisture profiles and structural changes during the drying and cooling of maize using MRI
Author(s)
Song, Huaipu
Issue Date
1991
Doctoral Committee Chair(s)
Litchfield, J. Bruce
Department of Study
Agricultural and Biological Engineering
Discipline
Agricultural and Biological Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Agricultural
Language
eng
Abstract
The purpose of this study was to nondestructively measure and analyze transient moisture profiles and associated structural changes during drying and cooling processes. Three yellow dent corn hybrids were measured during drying and cooling. Four drying temperatures, 27, 49, 71, and 93$\sp\circ$C, were used. Magnetic resonance imaging (MRI) was applied to nondestructively acquire proton images from the corn kernels during drying and cooling. A three-dimensional Fourier transform pulse sequence was used.
Moisture transfer in corn kernels during drying and cooling was analyzed from the 3D MR images. There were moisture gradients in corn kernels even at an equilibrium state before drying. There were two primary routes for moisture leaving a corn kernel during drying, one was through the corn surface, and the second was through the glandular layer of the scutellum. The rapid decrease of moisture from the endosperm near the primary moisture transfer routes generated moisture gradients in the surrounding areas. The largest moisture gradients were formed around the moisture transfer routes during drying. High drying temperatures caused rapid moisture decrease and higher moisture gradients in the corn kernels.
Stress cracks were measured at 27, 71, and 93$\sp\circ$C. Stress cracks initiated in the endosperm during drying. The initiation of stress cracks was associated with large moisture gradients and low moisture content. Cracks propagated from near the corn surface to the center of corn kernels during drying in most cases. Corn variety also affected the location of initiation of stress cracks. Cracks always occurred in the back of the FR618 x GH123 kernels but occurred either in the back or in the center of the FR27 x Mo17 kernels. Temperature affected the cracking propagation speed. At low temperatures, cracks developed slowly.
Single corn kernel drying-cooling curves, the spin-lattice and the spin-spin relaxation times of kernels during drying and cooling, temperature distribution in the corn kernels during drying, corn component water activity and moisture content, as well as the physical and chemical properties of the corn samples were also measured.
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