Rheology of starch nanoparticles as influenced by particle size, concentration and temperature

Abstract

Starch nanoparticles (SNP) were isolated from native starches of different botanical origins, showing comparable amylose contents but different crystalline types. The objective was to determine if variations in the morphology and thermal stability of SNP influences the aqueous rheology at room and elevated temperatures. A comparison of the particle size distribution of SNP, both in their dry state and in aqueous suspension at room and elevated temperatures, revealed substantial diversity in the thermal stability of SNP. The SNP from all starch sources were round in shape, but varied in their size distribution. At 5% (w/v) the SNP suspensions formed a thick paste that demonstrated a pseudoplastic behavior. The viscosity and viscoelastic behavior significantly varied among the starch sources as a function of shear, frequency and temperature. A model explaining the viscoelastic behavior of SNP has been proposed, which predicts the composition of both the continuous and dispersed phases. The data suggest that careful selection of processing conditions, such as heating temperature and shearing conditions, is required to achieve the target functionality of SNP in food and industrial applications.