不同小麦品种支链淀粉链长分配及其与淀粉理化特性的关系

以糯性与非糯性小麦品种（系）为材料，研究直、支链淀粉蓝值、支链淀粉链长分配及其与淀粉理化特性的关系。结果表明，直链淀粉的蓝值和最大吸收波长均显著大于支链淀粉；支链淀粉蓝值和最大吸收波长表现为中筋小麦＞弱筋小麦＞强筋小麦＞糯小麦，蓝值和最大吸收峰间呈极显著正相关，蓝值和吸收波长越大，说明支链淀粉含较长的支链。经Sephadex G75分离支链淀粉的支链，可得到3个组分，非糯小麦长B链(DP≥65.8)组分占支链淀粉百分含量最低，中等B链(29＜DP＜65.8)组分其次，短B链和A链(DP≤29)组分高达65%左右，前两个组分含量表现为弱筋小麦＞强筋小麦＞中筋小麦，且同一类型不同品种间也存在差异；而糯小麦未能洗脱出长B链。相关分析表明，除崩解值外，长B链与黏度各特征值均呈极显著正相关，与结晶度呈显著正相关，说明长B链含量显著影响淀粉的理化特性。

Chain Length Distribution of Debranched Amylopectin and Its Relationship with Physicochemical Properties of Starch in Different Wheat Cultivars

Starch and its pasting and retrogradation properties appear to be one of the key factors determining the qualities of wheat products. Amylopectin structure in starch granules can be described by a cluster model. The chain-length distribution of amylopectin has been focused in researches because of its relation to physicochemical properties of starch. The long B chains render the starch granule strong and resilient, thus leading to the firm texture of cooked rice, while the shortage of such chains leads to weak granules resulting in soft cooked rice. Now more and more researchers show their attentions to the relationship between the structure and physicochemical properties of starch. We mainly studied chain length distribution of amylopectin debranched by isoamylase in waxy and non-waxy wheat (Triticum aestivum L.) at Yangzhou University, also analyzed the relationships between starch structure and starch physicochemical properties, which would provide some information for producing wheat with good grain quality and high yield. The blue value (BV) and maximum absorption (λ_max) of amylose or amylopectin and the chain length distribution of debranched amylopectin were measured. The results showed that BV and λ_maxAM of amylose were higher than those of amylopectin. The order of BV and λ_max of amylopectin (λ_maxAP) was medium-gluten wheat>weak-gluten wheat>strong-gluten wheat>waxy wheat. There was a positive correlation between BV and λ_maxAP. Three kinds of components of debranched amylopectin molecular chain were got by Sephadex G75 from all different cultivars except waxy wheat cultivars. The weight percentage of long B-chain in debranched amylopectin was the lowest among three compositions, that of intermediate B-chain content was the second, that of short B-chain and A-chain contents accounting for about 65% were the highest. The order of long B-chain and intermediate B-chain percentage was weak-gluten wheat>strong-gluten wheat>medium-gluten wheat in normal types. Obvious differences among different cultivars in the same type were also observed. There was no long B-chain in amylopectin of waxy wheat. The proportion of long B-chain was highly significantly correlated with pasting parameters of RVA except breakdown (BD), and significantly correlated with crystalline degree. It might be assumed that physicochemical characteristics of starch in wheat grain were significantly affected by the long B-chain content.