Abstract
Diffusion-weighted magnetic resonance imaging was used to determine water diffusion coefficients (D) in hull-less barley kernel components (endosperm and embryo) at 20.5±0.5°C. The D values in barley components were time-dependent and restricted in nature as indicated by the decrease in the apparent diffusion coefficient with increasing diffusion time (from 3 to 25 ms). A four-parameter Padé approximation model was used to estimate D and pore geometry (pore surface area–to-volume ratio, pore size, porosity, electrical conductivity and permeability of water) of the barley components after long diffusion time (t → ∞) using data obtained during a relatively short period of diffusion. The D of embryo and endosperm were 2.2±0.07 × 10−5 mmCitation 2 /s and 1.0±0.10 × 10−5 mmCitation 2 /s, respectively. These D values were used to simulate moisture and temperature patterns during the drying of a barley kernel using a two-dimensional simultaneous heat and moisture transfer model and compared with literature D values for validation purposes. Based on the comparison, the D values of barley components obtained from our study can be used to develop realistic models of water transport in barley during different postharvest processing operations (e.g., drying, kilning, steeping).
ACKNOWLEDGEMENTS
This research was financially supported by the Canada Research Chairs program and the Natural Sciences and Engineering Research Council (NSERC) of Canada.