A magnetic resonance study of water uptake in whole barley kernels

The water uptake by barley kernels was followed by H-1 NMR spectroscopy. A model was used to explain the first 7 h of imbibition. Measurement of the 1 H spin-lattice relaxation rate, R-1, showed that during the first 7 h of im bibition, water uptake is dominated by a purely diffusive process with a ro otD . t dependence, where D is the diffusion constant and t is time. While increasing during the first 7 h of imbibition, R-1 slowly but continuously decreased afterwards. The observed changes in R-1 with imbibition time allo wed discrimination between the first two phases in water uptake, as general ly observed in germinating seeds. The second phase was characterized by a s low but continuous decrease in R-1, indicating a redistribution of water wi thin the kernel. Observed spin-lattice relaxation rates, R-1, were treated as a superposition of rates from water molecules in two different physical phases; a mobile and a less mobile phase. Using the Stokes-Einstein-Debye t heory for viscosity, the overall water viscosity within the kernel was dete rmined using the two-phase model to describe water mobility.