Characteristics of Starch from Opaque and Translucent Perisperm of Amaranth (A. hypochondriacus) Grains

Amaranth is a pseudocereal that has seen increasing production in recent decades. However, the physicochemical properties of amaranth starch have been scarcely studied. This work focuses on the characterization of amaranth starch from two different varieties. Amaranth starch was isolated from the perisperm of opaque and translucent amaranth (A. hypochondriacus) grains using a wet milling process. The starch granules in both cases show typical morphological features, with a polygonal shape and mean granule diameter of 1.5–2.5 µm. Starch from opaque perisperm is waxy, with an amylose content of 0.5%. In contrast, starch from a translucent perisperm presents a high amylose content of 14.9%. A DSC study shows a gelatinization enthalpy of 8.1–8.4 J g⁻¹ for both cases. The amylopectin molecular weight is higher for the opaque perisperm (7.0 × 10⁷ g · mol⁻¹) than for the translucent (6.2 × 10⁷ g · mol⁻¹) perisperm. In contrast, the radius of gyration is higher for the translucent perisperm (237 nm) than its opaque (222 nm) counterpart. The differences in the starch characteristics of translucent and opaque perisperm increase the potential of amaranth starch for diverse applications, from gluten-free bread to encapsulation systems.