Aqueous re-dispersibility of starch nanocrystal powder improved by sodium hypochlorite oxidation

In this study, the aqueous re-dispersibility of starch nanocrystal (SNC) powder was significantly improved by sodium hypochlorite (NaClO) oxidation, with more than 2% (w/w) active chlorine. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses verified the oxidation process of SNC. The oxidation degree (carboxyl groups content) increased from 0.41% to 0.581% (w/w) while the applied active chlorine increased from 1% to 4% (w/w). X-ray diffraction showed that NaClO oxidation induced minor destruction to SNC when the applied active chlorine exceeded 2%, and the relative crystallinity decreased from 45.6% to 42.8%. Due to the introduction of carboxyl groups, the zeta potential of oxidized SNC (OSNC, under 2% active chlorine level) suspension (re-dispersed from oven-dried OSNC powder) reached to -23 mV. Consequently, a high degree of individualized SNC with the particle size of 20 nm was obtained and the suspension maintained the stability for at least 20 days. (C) 2015 Elsevier Ltd. All rights reserved.