Three different transplanting dates for two rice cultivars grown in Daegu, Republic of Korea, were examined to identify the changes in growth, rice quality, and characteristics of amylopectin. An early transplanting date caused a reduction in the number of panicles in both rice cultivars compared to that in the optimal and late transplanting dates. The 1000-grain weight in the two rice cultivars was significantly increased in the late transplanting date. The rice cultivar tolerant to high temperatures, Donganbyeo, exhibited the lowest milky grain rate in the late transplanting date. The highest rate of head grain was observed in the late transplanting date in both rice cultivars. Regarding the pattern of pasting properties, peak viscosity increased with delayed transplanting dates. With respect to changes in the amylopectin branch-chain length distribution, the amylopectin structure of the translucent Dongan rice cultivar transplanted on April 25 was characterized by a significant increase in A chains with DP > 12, and a decrease in long chains DP ≥ 37 compared to that transplanted on June 25. In contrast, the amylopectin structure of the chalky Dongan rice cultivar transplanted on April 25 exhibited further decrease in 13 < DP < 19 than that transplanted on June 25. In the Ungwang rice cultivar, the amylopectin structure of the translucent Ungwang rice cultivar transplanted on April 25 and June 25 was characterized by a significant decrease in the lengths of total amylopectin chains. Furthermore, the amylopectin structure of the chalky Ungwangbyeo rice cultivar transplanted on April 25 was characterized by a significant increase in 7 < DP < 30, while a significant decrease was observed in that transplanted on June 25. These results indicate that the amylopectin structure is altered by different transplanting dates depending on the characteristics of the rice cultivar.

We investigated the physicochemical properties and starch structure of various rice varieties including 15 colored cultivars. NKHC showed the highest level of protein, lipid, and total dietary fiber levels. Reddish brown rice showed higher lipid content than that in black rice cultivars. Apparent amylose content of waxy and non-waxy colored rice varieties was within the range of 3~5% and 15~18%, respectively. IP exhibited the highest total starch (TS) content, whereas, NKHC and HJJ showed lower TS content than that in other cultivars. Pasting temperature of all colored rice cultivars, except IP, was about 68°C. Peak viscosity of IP, JJJ, Hong, and GGHM showed high values of 138, 130, 128, and 124, respectively. All the colored rice cultivars presented A-type X-ray diffraction pattern and polygonal shapes of starch granules were observed using scanning electron micrographs (SEM). Major groups of amylopectin chain lengths were B (12 < DP ≤ 24) and A (DP ≤ 12). SMHC showed the highest B chain content and the lowest A chain content (P < 0.05). These experimental results provided useful information for scientists and the food industry regarding colored rice starches.