Relationships between supramolecular organization and amylopectin fine structure of quinoa starch

Abstract The molecular and granular structure of 9 quinoa starches were investigated and correlated with each other. The molecular structure of quinoa amylopectin and β-limit dextrins studied by high performance anion exchange chromatography suggested that quinoa amylopectin contains a high amount of short chains. The average external chain length (ECL) and average internal chain length (ICL) of nine quinoa starch studied were 10.7 and 4.90 glucosyl residues, respectively. Small-angle X-ray scattering (SAXS) was applied to study the granular structure of quinoa starches. The average thickness of crystalline lamellae (dc) and amorphous lamellae (da) were 6.07 and 2.60 nm, respectively. Correlation analysis suggested that the amounts of short amylopectin chains were positively correlated with dc and they induced heterogeneity in the crystalline lamellae. The amount of long internal chains was positively correlated with da and they could stabilize the double helices in the crystalline lamellae. The correlation analysis based on individual chains suggested that current chain classification might lack a strong structural basis for the supramolecular organization of the granules. The correlations obtained in current research could be explained using the building block backbone model.