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.

The objective of this study was to evaluate quality properties, including amylopectin content, and texture analysis of brown rice and germinated brown rice cultivars in Korea for rice processing products. The amylopectin short chain content of germinated brown rice was significantly higher than that of brown rice. Texture analysis test showed that germinated brown rice Jinbo had the lowest hardness and toughness as well as and highest stickiness and adhesiveness. The correlation between degree of polymerization of amylopectin and texture analysis was also evaluated. In particular, germinated brown rice, short-chain amylopectin showed a negative correlation with hardness and toughness, whereas long-chain amylopectin showed a positive correlation with hardness, toughness, and adhesiveness. These results indicate that there is a relationship between degree of polymerization and texture analysis.

본 연구는 알카리붕괴도가 다른 황금누리벼, 일품벼, 상주벼, 태봉벼, 남평벼, 다산벼의 일반미 6품종의 아밀로펙틴 구조와 밥의 호화물성을 조사 하여 상관관계를 조사한 결과이다. 1. 6품종 쌀의 알칼리붕괴도는 황금누리벼의 7.0부터 다산벼의 5.0까지 고르게 분포하였다. 아밀로펙틴 구조 분석결과 시료는 모두 중합도 12에서 최고 분포를 갖는 등 비슷한 유형을 나타냈으며 알칼리붕괴도가 높은 품종은 중합도 15까지 짧은 사슬의 함량이 다른 품종에 비해 많이 함유하고 있는 것으로 나타났다. 2. 호화된 밥의 표면 경도는 다산벼, 일품벼, 황금누리벼의 순으로 컸으며 끈기는 일품벼가 가장 높게 나타났다. 밥의 전체 경도는 다산벼가 가장 높은 것으로 나타났고 다음으로 황금누리벼, 일품벼의 순으로 경도가 높은 것으로 조사되었다.

When GA4 was applied to heading stage, it was examined to understand the change of plant hormones and starch during grain filling and ripening. Exogenous gibberellin caused a dramatic decrease in endogenous ABA content. Endogenous GA4 content in both superior and inferior part was more promoted in GA4-treated rice grain than in the control. GA1 content of an inferior part was not detected in the control and GA4-treated rice otherwise GA4 was detected in all grain parts. Ripened grain rate in GA4-treated rice grain was lower than that of the control plant. Amylopectin from GA4-treated grain contained more very short chains with degree of polymerization (DP) between 4 and 8 than amylopectin from the control plant. It suggests strongly that fine structure of rice endosperm may be changed by exogenously applied GA4 in rice plants.

Thirty-eight glutinous rice varieties were classified into nine groups on the scatter diagram by the upper two principal components (56% contribution to the total information) based on eleven physicochemical characteristics including the viscograms and physical properties of cooked rice. The first principal component was the factor mainly associated with the viscogram characteristics of rice flour emulsion and the second was the factor chiefly related to the physical properties of cooked rice and water absorbability of rice grain. Indica glutinous rices were clearly distinguished from japonica ones by the first principal component score. Javanica glutinous rices were widely distributed on the intermediate zone between indica and japonica or on several japonica rice groups. Significant positive or negative correlations were found among water absorption rates of rice grain, physical properties of cooked rice, and viscogram characteristics of rice flour. Especially in japonica glutinous rices, the breakdown and setback viscosities of rice flour were closely associated with the alkali digestion value of milled rice and the stickiness of cooked rice. The frequency ratio of short glucose chains (A-chain) to intermediate glucose chains (B-chain), the ratio of B- chains to long glucose chains (C-chain) and the relative frequency of A- or B-chain fractions representing the amylopection structure of rice starch was closely associated with the breakdown and setback viscosities of rice flour