Impact on molecular organization of amylopectin in starch granules upon annealing

• Published in: Carbohydrate polymers 2013-10, Vol.98 (1), p.1045-1055
• Main Authors: Vamadevan, Varatharajan, Bertoft, Eric, Soldatov, Dmitriy V., Seetharaman, Koushik
• Format: Article
• Language: English
• Subjects: amylopectin; Amylopectin - chemistry; Amylopectin structure; Annealing; Applied sciences; arrowroot; barley; Biological and medical sciences; Canna; correlation; DSC; enthalpy; Exact sciences and technology; Food industries; Fundamental and applied biological sciences. Psychology; Gelatinization; gelatinization temperature; Glucan chain; glutinous rice; melting point; mung beans; Natural polymers; oats; Physicochemistry of polymers; potatoes; rye; sago; Starch and polysaccharides; Starch and starchy product industries; starch granules; tapioca; Thermal properties; Time Factors; Transition Temperature; waxy corn; yams
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2013.07.006

•Internal organization of amylopectin influences assembly of crystalline lamellae in starch.•Structural defects in starch crystal may be related to internal structure and length of external chains.•Annealing is a probe to visualize the organization of chains within the crystalline lamellae. 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, ptype 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.