Preparation and characterization of waxy maize starch nanocrystals with a high yield via dry-heated oxalic acid hydrolysis

In this study, we prepared waxy maize starch nanocrystals (SNCs) for the first time using dry-heated oxalic acid hydrolysis with or without ultrasonic treatment. The dry-heating treatment was subjected to oxalic acid hydrolysis to produce SNCs with a high yield of 89.6%. Dynamic light scattering showed that the size of the obtained SNCs was 46.58-197.15 nm, and the polydispersion index was 0.28-0.52. Atomic force microscopy investigation found that the SNCs had a major axis of about 211.5 nm and a height of about 9.4 nm. The thermogravimetric analysis revealed that the SNCs' thermal stability slightly improved compared with that of native starch. X-ray diffraction indicated that the produced SNCs preserved the A-type crystal form of native starch, with the relative crystallinities of 29.52%-42.44%. The newly fabricated SNCs have potential applications in agriculture, cosmetics, and advanced materials.