Potato starch nanocrystal preparation via supercritical carbon dioxide pretreatment combined with enzymatic hydrolysis

Abstract

In this work, starch nanocrystals were successfully produced from downgraded potatoes using enzymatic hydrolysis combined with a supercritical carbon dioxide pretreatment to improve the accessibility of the enzyme to the starches. Enzymatic hydrolysis was carried out using the pullulanase enzyme at a temperature of 60 °C and a pH of 4. Following hydrolysis, the starch nanoparticles were recovered via precipitation and recrystallization. Comparative characterization of the native, supercritical carbon dioxide-pretreated, and hydrolyzed-recrystallized starch materials was conducted via transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The scanning electron microscopy images revealed alterations, e.g., layered strips, on the surface of the potato starch granules after the supercritical carbon dioxide pretreatment. The transmission electron microscopy images revealed that spherical nanostructures from 80 nm to 150 nm were successfully produced. The Fourier transform infrared spectroscopy spectra displayed several absorption bands corresponding to the molecular structure of starches. The X-ray diffractograms exhibited a typical B-type scattering pattern for all the samples. In addition, it was found that the crystallinity of the potato starch nanoparticles was considerably increased compared with native starch.