Nanostarch production by enzymatic hydrolysis of cereal and tuber starches

Abstract

In this work, nanostarch was extracted from cereal (maize) and tuber (potato and cassava) crops by an enzymatic process and characterized. Simultaneously, the conventional acid hydrolysis process was carried out to produce nanostarch. These nanostarches were characterized by different techniques such as dynamic light scattering (DLS), fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The smallest size was achieved in the case of maize starch, 18 ± 3 nm by acid hydrolysis and 162 ± 23 nm by the enzyme hydrolysis. The nanostarch yields by enzymatic process were 18, 29 and 41 wt% for maize, potato and cassava starches, respectively. Significant reduction in the crystalline region of starch was observed after enzyme hydrolysis, as analyzed by relative crystallinity using XRD spectra. The reduction of amorphous region in nanostarch decreased its melting enthalpy as demonstrated by DSC. Enzyme hydrolyzed nanostarch could find its potential application as fillers not only for their reinforcing properties in biocomposites but also for its renewability and biodegradability.

Keywords

• Acid hydrolysis
• α-Amylase
• Crystallinity
• Nanostarch, Scanning electron microscopy (SEM)
• Transmission electron microscopy