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Analysis of crystals of retrograded starch with sharp X-ray diffraction peaks made by recrystallization of amylose and amylopectin

Lian, Xijun, Cheng, Kaili, Wang, Danli, Zhu, Wei, Wang, Xueqing
International journal of food properties 2017 v.20 no.sup3 pp. S3224
X-ray diffraction, amylopectin, amylose, crystal structure, crystallization, crystals, differential scanning calorimetry, mixing, molecular weight, nuclear magnetic resonance spectroscopy, retrogradation, sweet potato starch, sweet potatoes
Retrogradation is a common occurrence of starchy food and many methods have been tried to retard it. Uncovering the crystalline structure of retrograded starch provides us the necessary information to get an effective method. In this paper, the crystals of retrograded sweet potato starch with sharp X-ray diffraction peaks were obtained by blending sweet potato amylose and amylopectin with narrow distribution of molecular weight. The 2θ angles of those crystals were at 14.7°, 20.7°, 24.3°, 26.5°, and 29.9°. Intervals between two branched chains in retrograded amylose were 0.606, 0.348 nm, and in retrograded amylopectin 0.336 nm. A possible mechanism for the formation of those crystals was proposed based on analyzing ¹H NMR, ¹³C NMR, X-ray diffraction, and differential scanning calorimeter of those samples. Cocrystallized amylose and amylopectin was necessary to prepare crystals of retrograded starch. More ordered arrangements exist in retrograded starch of sweet potato amylose and amylopectin.