Isolation and characterisation of nanoparticles from tef and maize starch modified with stearic acid

Wokadala O Cuthbert; Suprakas S Ray; Naushad M Emmambux

doi:10.1016/j.carbpol.2017.03.067

Isolation and characterisation of nanoparticles from tef and maize starch modified with stearic acid

Carbohydr Polym. 2017 Jul 15:168:86-93. doi: 10.1016/j.carbpol.2017.03.067. Epub 2017 Mar 22.

Authors

Wokadala O Cuthbert¹, Suprakas S Ray², Naushad M Emmambux³

Affiliations

¹ Department of Food Science, Old Agricultural Building (Building 46), University of Pretoria, Lynwood Road, Private bag X20 Hatfield, 0028 Pretoria, South Africa.
² DST/CSIR Nanotechnology Innovation Centre, National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa.
³ Department of Food Science, Old Agricultural Building (Building 46), University of Pretoria, Lynwood Road, Private bag X20 Hatfield, 0028 Pretoria, South Africa. Electronic address: naushad.emmambux@up.ac.za.

PMID: 28457467
DOI: 10.1016/j.carbpol.2017.03.067

Abstract

Nanoparticles were isolated from tef and maize starch modified with added stearic acid after pasting at 90°C for 130min. This was followed by thermo-stable alpha-amylase hydrolysis of the paste. The resultant residues were then characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic laser scattering particle size distribution (DLPSD), atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM). XRD and DSC showed that the isolated residues consisted of amylose-lipid complexes. These complexes were type II with melting temperature above 104°C. DLPSD, AFM and HRTEM showed that the isolated tef and maize starch residues consisted of nanoparticles which became more distinct with increased hydrolysis time. The isolated tef and maize nanoparticles had distinct particles of about 3-10nm and 2.4-6.7nm, respectively and the yield was about 24-30%. The results demonstrated that distinct (physically separate) nanoparticles of less than 10nm can be isolated after formation during pasting of tef and maize starch with stearic acid. The production and isolation of the nanoparticles uses green chemistry principles and these nanoparticles can be used in food and non-food systems as nanofillers.

Keywords: Amylose lipid complexes; Maize starch; Starch hydrolysis; Starch nanoparticles; Teff starch; V-amylose.