The structural characteristics of starches and their functional properties

Starch is composed of amylose and amylopectin and deposited as granules of different sizes and shapes with semi-crystalline and amorphous concentric layers that show the maltese cross'. Starches from different sources show variable chemical composition as well as the structure of their components that are involved in thermal properties. Amylose, lipids, phosphorylated residues and long lateral chain amylopectin interact among them avoiding water uptake. In contrast, high amylopectin contents, especially with short lateral chains, allow hydration via hydrogen bonds to form gels with the tendency to retrogradation. Smaller starch granules have a larger superficial area, surface pores, and channels that enhance water uptake. High hydration increases the swelling, viscosity, and gelatinization ability of starch granules. The knowledge of those properties allows the selection of the most appropriate starch for a specific end use. This review discusses the relationship between the physicochemical composition of the starch and their rheological properties.