Influence of nanoprecipitation on crystalline starch nanoparticle formed by ultrasonic assisted weak-acid hydrolysis of cassava starch and the rheology of their solutions

In this research, plant and fruits extracts were used for the first time to synthesize crystalline starch nanoparticles (CSNP). The physical properties of the CSNP including their size distribution, crystalline structures were investigated. The isolation, recovery yield and the influence of the process variables were studied. The rheological behaviours of the CSNP were compared and contrasted with the native cassava starch (CS) and commercial polymer xanthan. The combined method of weak-acid hydrolysis, ultrasonic and nanoprecipitation were effective in producing spherical and polygonal nanoparticles with a mean diameter of 100 nm, increased yield of 39% and increased in crystallinity of 7% respectively. The CSNP, CS and xanthan exhibited shear-thinning and pseudoplastic behaviour. The R-2 value for the model is very close to unity indicating a perfect fit. Indicating that the power law model best describes the rheological behaviour. Cavitation, nucleation and crystals growth were the dominant mechanism that influenced the formation of CSNP. Whereas, concentration, morphology and the surface charge of the solutions were the main factors that influenced the rheology of the system. The viscosity increased with increase in surface area and temperature of the CS and CSNP in contrast to a decrease in viscosity as the temperature of xanthan increases.