When a rice kernel fissures, it can break in subsequent food processing operations and lose its commercial value. Head rice yield (HRY) is a measure of the percent of kernels that remain whole (at least three-fourths of original length) after rice has been milled. Our experiment was designed to test the effect of a rapid state transition during drying and tempering processes using cultivars Bengal and Cypress. ‘Bengal’ is a medium-size kernel and ‘Cypress’ is a longsize, thinner grained cultivar. Immediately after drying, the rice samples were separated into four sub-samples and tempered for 0, 80, 160, or 240 minutes at the temperature of the drying air. Tempering is a process to allow kernel moisture content gradients to decrease, thereby reducing the stress within the kernel. From each sample, 400 kernels were randomly selected, visually observed, and the percentage of fissured kernels determined. Results showed that the percentage of fissured kernels generally decreased with tempering. However, some samples still showed many fissures even after extended tempering, yet had a high HRY. While HRY is currently the primary index of rice quality, it is known that fissured kernels can severely and detrimentally affect end-use processing operations such as cooking or puffing. Thus, the tempering duration required for preventing kernel fissuring might be longer than the tempering duration required for maintaining a high HRY.
Jimenez, Monica J.; Siebenmorgen, Terry J.; and Cnossen, A. G.
"Correlating fissure occurrence to rice quality for various drying and tempering treatments,"
Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences. University of Arkansas System Division of Agriculture. 2:27-32.
Available at: http://scholarworks.uark.edu/discoverymag/vol2/iss1/8