Abstract
NMR imaging has been used to study the boiling and steaming of intact
wheat grains by mapping the distribution of water on the central
cross section of grains after various cooking times. The results
show different distributions of water occurring with boiling and
steaming. Boiled grains showed a front of moisture which gradually
moved towards the centre of the grain, although some water was able
to diffuse ahead of the front. Steamed grains showed no such front,
but showed a homogeneous distribution of water which gradually increases
with cooking time. The different results for boiling and steaming
imply that different mechanisms control the influx of water in each
case, and provide important data for modelling these processes. It
is postulated that absorption of water during steaming is slowed
by the grain temperature rising above that of the steam temperature
as a result of the latent heat associated with the condensation of
steam being taken up by the grain.
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