3.4. Relationship between visual surface cracking degree and
14 1 Month :
CHN
SPT
KML
surface color change 1 Year : CHN SPT KML
The color of the rice kernel surface revealed the accumulation of red-violet betacyanins, as determined by the degree of colorimetric change from the native white rice kernel color, DE. It was observed that DE values were increased with an increased degree of surface cracking (Fig. 4). This evidence demonstrates that larger accumu- lations of betacyanins into the rice kernels occur in response to larger degrees of surface cracking. The different rice varieties and storage time periods showed similar relationships between DE values and surface cracking degrees (similar slopes of the curves); suggesting a similarity of color increment on the surface of these rice kernels.
However, the DE values of the surfaces of rice kernels which had
been stored for one month differed from those stored for one year. This is thought to be due to the difference in their native kernel colors before the treatments. Normally, white rice kernels gain yellowish color as they are stored, due to the Maillard reaction (Marshall & Wadsworth, 1999).