Preparation and characterization of starch nanocrystals combining ball milling with acid hydrolysis

Waxy maize starch was mechanically treated with a planetary ball mill. X-ray diffraction analysis was employed to determine the optimal ball milling time. After ball milling, the pretreated starch was hydrolyzed with H2SO4. The hydrolysates were obtained and their relative crystallinity, morphology, and particle size were estimated by X-ray diffraction analysis, atomic force microscopy, and nanoparticle size analyzer, respectively. The results revealed that it is possible to obtain starch nanocrystals (SNCs) after a combination of ball milling and 3 days of H2SO4 hydrolysis with a yield of 19.3 wt% with a shape similar to those acquired by the conventional procedure after 5 days of sulfuric acid hydrolysis, with a yield of 15.8 wt%. Round-edge SNCs with an average diameter of approximately 31 nm were observed. The results revealed that by controlling some parameters, certain mechanical processing methods considered unsuitable could also be applied to the preparation of SNCs.