Long-term retrogradation of amylopectin always leads to the quality deterioration of starch-based food. In this paper, the purified maize amylopectin was co-crystallized with NaCl to obtain anti-retrograded amylopectin. The results showed that the retrogradation rate of maize amylopectin dropped directly from 27.92 % to 19.05 % at the conditions of amylopectin: 5 % NaCl (m/v) = 1.7:10, eutectic times 24 h at 4 °C. The co-crystals with a dendritic shape consisted of a center and several large branches and the length of the largest branch reached up to 10,000 μm. The results of the maximum absorbance of iodine-attached amylopectin, molecular weight and chain length distributions showed that hydrolysis and graft of amylopectin happened in the eutectic process. Residues produced by acid hydrolysis linked to the main chains via α-1,6 glycosidic linkage at the late stage of eutectic reaction. The marked signs for single helix of maize amylopectin with Mw >20 × 105 g/mol were the enhancement of weak resonance at 100.0 ppm (104.1, 100.0, 94.6, 82.9 ppm). Single-helix maize amylopectin was more likely to form sharp X-ray diffraction during being dried without gelatinization. The possible mechanism for anti-retrogradation of maize amylopectin by co-crystal treatment was deduced. Co-crystallization with NaCl to produce single-helix amylopectin was a promising strategy to prepare anti-retrogradation amylopectin.
Keywords: Chain length distribution; Co-crystallization; Maize amylopectin; Retrogradation rate; Solid (13)C NMR.
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