Food Science Department, University of Guelph, Canada.
Carbohydr Polym. 2013 Oct 15;98(1):1045-55. doi: 10.1016/j.carbpol.2013.07.006. Epub 2013 Jul 12.
This study investigated the influence of the internal structure of amylopectin on annealing (3h, 24h) of starches from four different types of amylopectin (Bertoft, Koch, & Aman, 2012; Bertoft, Piyachomkwan, Chatakanonda, & Sriroth, 2008). Regardless of the starch source and incubation time, annealing significantly increased the onset gelatinization temperature (To) and narrowed and deepened the amylopectin endotherm. However, the extent of the change in the melting temperature (Tm) and the enthalpy of gelatinization (ΔH) differed among the types. In terms of the To and Tm, starches from type 1 (oat, rye, barley, and waxy barley) showed the most significant response to annealing. The Tm of starches belonging to type 2 (waxy maize, rice, waxy rice, and sago) remained unchanged after 3h of annealing. Type 1 and type 2 starches with the lowest gelatinization temperatures showed the greatest increase in melting temperature after annealing. However, type 3 (tapioca, mung bean, and arrowroot) and type 4 (potato, waxy potato, canna, and yam) starches were not in line with these observations. Instead, starches from type 3 and type 4 showed a pronounced increase in the ΔH. The inter-block chain length (IB-CL) (distance between tightly branched units within a cluster) correlated positively (r=0.93, p<0.01) with the change in enthalpy after 24h of annealing. These data indicate that a short IB-CL affects the optimum registration of double helices within the crystalline lamellae. The relationship between the gelatinization parameters before and after annealing suggests that type 1 and 2 starches might possess a high number of unpacked double helices (type 1>type 2) compared to other types. Longer IB-CLs, which facilitate the parallel packing of splayed double helices, and the lengthening of double helices likely increased the ΔH in type 3 and type 4 starches. It is concluded that annealing can be used as a probe for visualizing the organization of glucan chains (alignment of double helices/degree of perfection) within crystalline lamellae.
这项研究调查了支链淀粉内部结构对四种不同类型支链淀粉（Bertoft、Koch 和 Aman，2012；Bertoft、Piyachomkwan、Chatakanonda 和 Sriroth，2008）退火（3h、24h）的影响。无论淀粉来源和孵育时间如何，退火都会显著增加起始糊化温度（To），并使支链淀粉的吸热峰变窄加深。然而，不同类型的熔融温度（Tm）和糊化焓（ΔH）的变化程度有所不同。就 To 和 Tm 而言，来自类型 1（燕麦、黑麦、大麦和蜡质大麦）的淀粉对退火的反应最为明显。在 3h 的退火后，属于类型 2（蜡质玉米、大米、蜡质大米和西米）的淀粉的 Tm 保持不变。具有最低糊化温度的类型 1 和类型 2 淀粉在退火后熔融温度的增加最大。然而，类型 3（木薯、绿豆和葛根）和类型 4（马铃薯、蜡质马铃薯、美人蕉和山药）的淀粉则不符合这些观察结果。相反，类型 3 和类型 4 的淀粉的 ΔH 显著增加。间块链长（IB-CL）（簇内紧密分支单元之间的距离）与 24h 退火后焓的变化呈正相关（r=0.93，p<0.01）。这些数据表明，短的 IB-CL 会影响结晶层内双螺旋的最佳排列。退火前后的糊化参数之间的关系表明，与其他类型相比，类型 1 和 2 淀粉可能具有更多未展开的双螺旋（类型 1>类型 2）。较长的 IB-CL 有利于伸展的双螺旋的平行堆积，以及双螺旋的延长，可能会增加类型 3 和类型 4 淀粉的 ΔH。结论是，退火可以用作可视化结晶层内葡聚糖链组织（双螺旋排列/完善程度）的探针。
