Evaluation of rheological behavior of starch nanocrystals by acid hydrolysis and starch nanoparticles by self-assembly: A comparative study

The rheological properties of suspensions containing starch nanocrystals (SNCs) and starch nanoparticles (SNPs) under different ionic strength conditions were measured and contrasted. SNCs were produced through sulfuric acid (H2SO4) hydrolysis, and SNPs were prepared by the self-assembly of short-chain amylose. At a concentration of 5% (w/v) nano-scale starch particles, the viscosity of the SNC suspensions was much higher than that of the SNP suspensions. When the ionic strength was increased from 0 to 14.0 mM sodium chloride (NaCl), the viscosity of the SNC suspensions increased markedly. However, the viscosity of the SNP suspensions did not change noticeably even at high ionic strengths (10.5 -256.0 mM). When the ionic strength increased, the linear viscoelastic range of the SNC suspensions improved, while that of the SNP suspensions changed little. Increasing the ionic strength in the SNC suspensions increased the storage modulus and loss modulus. Meanwhile, the temperature of the gel increased significantly when it changed from the elastic to the viscous state, indicating that the presence of NaCl enhanced the heat stability of the SNC suspensions. The gelling properties of SNP suspensions containing 10.5 mM NaCl were improved, whereas those of other suspensions with higher ionic strength were weakened. In the SNC suspensions, the magnitude of storage modulus and loss modulus did not change when the angular frequency increased, indicating the formation of a strong elastic gel. In contrast, the loss angle tangent of the SNP suspensions was more than 1, suggesting that the SNP suspensions tended to be fluid. (C) 2015 Elsevier Ltd. All rights reserved.