The effect of moisture content (MC) on the glass transition temperature (T-
g) of individual brown rice kernels of Bengal, a medium-grain cultivar, and
Cypress, a long-grain cultivar, was studied. Three methods were investigat
ed for measuring T-g: differential scanning calorimetry (DSC), thermomechan
ical analysis (TMA), and dynamic mechanical analysis (DMA). Among these met
hods, TMA was chosen, because it can also measure changes in the thermal vo
lumetric coefficient (beta) of the kernel during glass transition. TMA-meas
ured T-g at similar MC levels for both cultivars were not significantly dif
ferent and were combined to generate a brown rice state diagram. Individual
kernel T-g for both cultivars increased from 22 to 58 degreesC as MC decre
ased from 27 to 3% wb. Linear and sigmoid models were derived to relate T-g
to MC. The linear model was sufficient to describe the property changes in
the MC range encountered during rice drying. Mean beta values across both
cultivars in the rubbery state was 4.62 x 10(-4)/degreesC and was higher th
an the mean beta value of 0.87 x 10(-4)/degreesC in the glassy state. A hyp
othetical rice drying process was mapped onto the combined state diagram ge
nerated for Bengal and Cypress.