Effect of pHs on dispersity of maize starch nanocrystals in aqueous medium

• Starch nanocrystals were prepared by H2SO4-hydrolysis.
• Effect of pHs on dispersity of starch nanocrystal was examined.
• Dispersity of starch nancrystal suspension was controlled by adjusting pH.

The effect of different dispersion pHs on zeta potentials, size distribution, and aggregation behavior of starch nanocrystals (SNC) prepared by sulfuric acid hydrolysis was examined in this study. The results showed that zeta potential of starch nanocrystals decreased from −6.7 mV to −34.5 mV as the dispersion pH increased from 2.07 to 11.96. Smaller starch nanocrystals and wider distribution peaks were observed with the increase of dispersion pH. The data obtained from field emission scanning electron microscopy (FE-SEM) also indicated that the aggregated parallelepiped nanoplatelets (1.5 μm) changed to monodispersed spherical-like nanoparticles (50 nm) with increasing of dispersion pH from 2.07 to 11.96. Considering these findings, the stable SNC suspension could be obtained by adjusting the dispersion pH to the range of 7.44–9.45.

Carboxyl and sulfate esters groups were present on the surface of starch nanocrystals after H2SO4-hydrolysis. The groups were in protonated state under acidic conditions, while the dispersion medium became alkaline, carboxyl groups and sulfate esters were deprotonated and the repulsive forces were strong enough to make starch nanocrystals suspension stable.Figure optionsDownload as PowerPoint slide