College of Food Science, South China Agricultural University, 483, Wushan Road, Guangzhou 510642, China.
Molecules. 2018 Dec 10;23(12):3262. doi: 10.3390/molecules23123262.
Starch was isolated from longan seeds of three widely distributed cultivars (Chuliang, Shixia, and Caopu) in China. Comparisons of the multi-level structure of the starch of longan seeds among various cultivars were made, and the relations between these structural and property characteristics are discussed. The isolated starch, accounting for 44.9⁻49.5% (/) in longan seeds, had an oval or an irregular polygonal shape with a smooth surface. Their chain-length distributions (CLDs) varied with longan cultivar; Chuliang showed a larger proportion of longer amylopectin chains with a degree of polymerization (DP) 30~100. This is attributed to the slightly higher relative crystallinity of Chuliang longan seed starch. Apparent differences were also detected in amylose structure. Caopu showed a higher amylose content than Chuliang and Shixia, resulting in its lower gelatinization temperatures and enthalpy change. All longan seed starch had a typical A-type crystal structure with relative crystallinity ranging 28.6⁻28.9%. For raw starch, Caopu showed the lowest digestion rate, followed by Chuliang; Shixia showed the highest. This is because Caopu had the highest amylose content. Chuliang had a more intact structure than Shixia, as suggested by its higher crystallinity, although they had similar amylose content. After being fully gelatinized, all starch showed a similar digestion process, indicating that the digestibility of gelatinized starch does not differ with starch source or structure.
龙眼种子淀粉的分离及其特性研究
从中国三个分布广泛的龙眼品种（储良、石硖和草铺）中分离出淀粉。比较了不同品种龙眼种子淀粉的多层次结构，并探讨了这些结构和特性之间的关系。分离出的淀粉占龙眼种子的 44.9⁻49.5%（/），呈椭圆形或不规则多边形，表面光滑。它们的链长分布（CLD）随龙眼品种而异；储良表现出更长的支链淀粉链的比例较大，聚合度（DP）为 30~100。这归因于储良龙眼种子淀粉的相对结晶度略高。直链淀粉结构也存在明显差异。草铺的直链淀粉含量高于储良和石硖，导致其糊化温度和焓变较低。所有龙眼种子淀粉均具有典型的 A 型晶体结构，相对结晶度为 28.6⁻28.9%。对于原淀粉，草铺的消化率最低，其次是储良；石硖的消化率最高。这是因为草铺的直链淀粉含量最高。储良的结构比石硖更完整，这表明其结晶度较高，尽管它们的直链淀粉含量相似。完全糊化后，所有淀粉的消化过程相似，表明糊化淀粉的消化率不因淀粉来源或结构而异。
