Extraction of nanostructured starch from purified granules of waxy and non-waxy barley cultivars

Waxy and non-waxy barley flours were selected as native material for the extraction, by acidic hydrolysis, of starch nanoparticles (NPs), with the main aim of evaluating how their different amylose/amylopectin ratio affected NPs structural characteristics. To this scope, two approaches based, respectively, on the use of NaCl/toluene (called organic treatment) and of sodium hydroxide solutions (called alkali treatment) were adopted in order to purify the waxy flours to give starch granules. Morphological investigations of waxy flour after alkali and organic treatments, before and after acetone washing, showed that the isolation methods of the starch did not affect the general morphologic characteristics of starch granules. The method found to provide the best outcomes in terms of thermal and morphological properties was also applied to purify the non-waxy barley. The results confirmed that waxy starch characterized by granules of smaller dimensions (WS) gave amorphous nanoparticles (WNP) with reduced mean diameter and thermal stability with respect to NPs obtained from non-waxy barley flour.