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Viscoelastic properties and the glassy state in soybeans

Published online by Cambridge University Press:  19 September 2008

K. S. Maki
Affiliation:
Department of Agricultural and Biological Engineering, Cornell University, Ithaca, NY 14853, USA.
J. A. Bartsch
Affiliation:
Department of Agricultural and Biological Engineering, Cornell University, Ithaca, NY 14853, USA.
R. E. Pitt
Affiliation:
Department of Agricultural and Biological Engineering, Cornell University, Ithaca, NY 14853, USA.
A. C. Leopold*
Affiliation:
Boyce Thompson Institute for Plant Research, Ithaca, NY 14853, USA
*
* Correspondence

Abstract

The cytoplasm of soybean seed axes is known to undergo a glass transition as moisture content decreases. In this study we have investigated whether the glass transition is reflected in the macroscopic mechanical properties of the seeds. Constant-deformation-rate compression tests and constant-deformation relaxation tests were performed with a cylindrical indenter on soybean cotyledons equilibrated to moisture contents ranging from 2% to 16% (dry basis). The apparent modulus of elasticity was found to rise sharply as moisture content declined below 10%, showing an inflection point at 9.8%, and a relatively constant elasticity below 7%. Other measures of mechanical behaviour were also constant in the drier ranges, including linear deformation, and plastic deformation. Each of these viscoelastic characteristics showed an inflection point or a departure from a linear function in the region of 7.5–9.8% moisture content, the hydration region below which the tissue is in a glassy state. It is suggested that the viscoelastic qualities of dry soybeans are principally a consequence of the tissues being in the glassy state.

Type
Research papers
Copyright
Copyright © Cambridge University Press 1994

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