Characterization of orange-fleshed sweet potato starch nanoparticles produced by acid hydrolysis

Abstract

Sweet potatoes are abundant in starch and have several applications for this component. Starch can be chemically changed to boost its beneficial properties. The objective of this study is to use common, easily accessible, and reasonably priced organic acids to produce modified starch with a nanoscale size from orange-fleshed sweet potato (OFSP). The characterization of OFSP nanostarch were assessed using hydrolysis with three distinct acids (acetic, citric and lactic acid) at concentrations ranging from 5 to 15 %. It was observed that nanostarch's swelling ability and viscosity decreased but its solubility increased during acid hydrolysis. OFSP nanostarch hydrolyzed with 10 % citric acid had a good recovery efficiency and quality suitable. Some physico-chemical properties of OFSP nanostarch were determined. Scanning electron microscopy and transmission electron microscopy were observed. The size of OFSP nanocrystals is in the range of 900–930 nm. The Fourier transform infrared (FTIR) spectrum of acid-treated starch contained 22 spectral peaks ranging from 3282.84 cm⁻¹ to 418.55 cm⁻¹, which indicated the vibrations of glycosidic bonds, hydroxyl groups, and CO bonds. Differential scanning calorimetry investigation revealed that sweet potato starch nanocrystals gelatinized at temperatures ranging from 65.4 to 89.1 °C. OFSP starch nanocrystals from acid-treated starch samples exhibited peaks at diffraction angles 2θ around 10°, 11°, 15°, 17°, 18°, 20°, and 23°. Producing nanostarch from OFSP starch not only raises the usage value of this raw material in the producing areas, but it also adds to the long-term development of this resource when the resulting products are well and widely used in various domains.