Molecular structure and architectural characteristics of outer shells and inner blocklets of normal and waxy wheat A- and B- starch granules

Abstract

Outer shells and inner blocklets were isolated from normal and waxy wheat A- and B- starch granules. Microstructural, molecular, and architectural characteristics of the isolated shells and blocklets were investigated using different methods and techniques. The results revealed that the outer shells were flake and net pocket shaped, with a compact surface and mass fractal. On the other hand, inner blocklets exhibited spherical, beaded, and rod shapes with a typical V-type crystalline structure. Crystallinity, degree of short-range order, amylopectin and amylose molecular weight, amount of intramolecular hydrogen bonds, and the average of shorter semicrystalline lamellae repetition distance varied between outer shells and inner blocklets, as well as depending on the type of wheat starch granules, i.e. normal and waxy wheat A- and B- starch granules. The branch chain length distribution of amylopectin affected the thickness of amorphous and crystalline regions, and the crystal order degree influenced the fractal and morphological characteristics of outer shells and inner blocklets. Additionally, amylose and amylopectin of inner blocklets were polymerized to form larger amylose and amylopectin molecules and develop the outer shells. The obtained findings give a theoretical basis for understanding the relationship between molecular structure and architectural characteristics of starch.