Water absorption in individual white-core and non-white-core grains of rice varieties used in sake
brewing was observed during soaking by magnetic resonance imaging (MRI). Water was absorbed faster
in white-core grains than in non-white-core grains and was pooled in the core. Moisture distributions
were compared using the line profiles of nuclear magnetic resonance signal intensities (SI profiles)
generated from magnetic resonance images of grains soaked for 2 h. SI profiles of white-core and nonwhite-
core grains overlapped despite slight differences in the central and intermediate regions of the
grains. A white-core-like structure with loosely packed starch granules was found to exist in the
endosperm of non-white-core grains. SI profiles of grains polished to 70% of the yield weight of brown
rice were similar in shape to those of grains polished to 90% of the yield, but their overall moisture
content was higher after the removal of the hydrophobic grain periphery. A varietal difference in the
thickness of the intermediate region, which may affect fissuring resistance in the polishing process, was
detected in SI profiles. Differences in water absorbability between parents and their offspring were also
apparent from their SI profiles. MRI enabled the detection of variety-specific water-absorption properties
in grains.