The glassy state and accelerated aging of soybeans

Deteriorative changes in seeds may be expected to reflect changes in physical state as well as in chemical composition. In the present study, measurements of changes in glass transition, lipid phase transition and sugar content were made during accelerated aging of two cultivars of soybeans ( Glycine max Merrill cv. Chippewa 64 and cv. Hodgson 78). The glass transition in axes, as measured by the thermally stimulated depolarization current method, showed gradual decreases in both magnitude and transition temperature during accelerated aging, and eventually, axes of seeds lost their ability to enter the glassy state. Sucrose, raffinose and stachyose contents in seed axes showed little or no change during the aging treatment. Membrane lipids in aged axes retained the liquid crystalline phase during aging. These data suggest that the changes of glass transition during accelerated aging occurred without associated changes in soluble sugar contents or changes in the liquid crystalline state of membrane lipids. The loss of the glass transition during accelerated aging could be a consequence of the annealing effect due to elevated temperature and moisture content. We propose that a loss of the glassy state during accelerated aging leads to an enhanced rate of subsequent deteriorative reactions in seeds and accelerates the loss of viability.