Starch nanoparticles resulting from combination of dry heating under mildly acidic conditions and homogenization

To modify starch granular structure, normal maize starch was subjected to dry heating with various amounts of 1.0 M HCl (1.2, 1.4 or 1.6 mL) and different treatment times (2, 4 or 8 h). For all reaction conditions, at least 80% of the starch substance was recovered, and amylose and amylopectin B1 chains were preferentially cleaved. As acidic condition and/or treatment time increased, the treated granules were readily fragmented by homogenization. The treatment appeared to alter short-range crystalline structure (FT-IR), but long-range crystalline structure (XRD) remained intact. Homogenization for 60 min fragmented the treated starch granules (subjected to reaction condition of 1.4 mL/4 h, 1.6 mL/2 h, and 1.6 mL/4 h) into nanoparticles consisting of individual platelet-like and spherical particles with diameters less than 100 nm. However, the fragmentation caused obvious damage in the long-range crystalline structure of starch nanoparticles, while the short-range chain associations remained relatively intact.