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MOISTURE DIFFUSION COEFFICIENTS OF SINGLE WHEAT KERNELS WITH ASSUMED SIMPLIFIED GEOMETRIES: ANALYTICAL APPROACH

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASAE.  VOL. 43(6): 1653-1659 . (doi: 10.13031/2013.3065) @2000
Authors:   S. Kang, S. R. Delwiche
Keywords:   Wheat, Moisture, Diffusion, Tempering

Using a combination of soaking data and an analytical solution of the diffusion equation, moisture diffusion coefficients of single wheat kernels were determined for nine commercial varieties representing six market classes of U.S. wheat. Two geometric conditions, the whole kernel as a prolate spheroid, and the endosperm (also modeled as prolate spheroidal) and pericarp as separate components, were examined. Values from the analytical solution for a sphere were adjusted by a geometrical correction factor to more closely represent the response of a prolate spheroid. The ranges in diffusion coefficients were 0.39 10 10 to 1.04 10 10 m 2 /s for endosperm and 0.04 10 10 to 0.28 10 10 m 2 /s for pericarp. Compared to the pericarp, moisture diffused more rapidly in the endosperm. Soft wheats tended to have a more permeable pericarp layer than hard wheats, which resulted in a greater overall rate of diffusion, despite the endosperm of these two groups being nearly equivalent in diffusion coefficient value.

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