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In this study, the cassava starch was micronized in a vacuum ball-mill to make tiny granules of different particle sizes (the d50 value from 7.9 μm to 24.0 μm). The properties of the micronized cassava starch, such as granularity, gelatinization properties, and dispersibility in organic solvent, have been evaluated. Then the micronized cassava starch has also been modified using a dry-method to improve its hydrophobic property, with aluminate coupling agent (ACA). The results suggest that the granularity of the starch decreases sharply through micronization in the vacuum ball-mill. The d50 value of micronized starch was reduced from 24.0 μm to 7.9 μm with the milling time from 0 h to 54 h. The active sites increase as the size of the cassava starch is reduced. The micronized starch has been found to be more easily gelatinized, dispersed in organic solvent and modified. The gelatinization temperature of starch was reduced from 59° C to 23° C with the milling time from 0 to 54 h. [ABSTRACT FROM AUTHOR]

Abstract: The granule morphology, microstructure, and thermal properties of micronized cassava starch prepared by a vacuum ball-grinding machine were investigated. Scanning electron microscopy (SEM) analysis indicated that the morphology of starch granule changes during the ball-grinding treatment. Differential scanning calorimetry (DSC) analysis indicated that the maximum peak temperature (T p) of the gelatinization process, the glass transition (T g), and peak height index (PHI) for the starch granules decreased when the size of micronized starch granules was reduced. When the size of starch granules was reduced beyond 9.11μm, they have a tendency to agglomerate and their ΔH were increased. The granule size has a significant effect on the gelatinization properties of cassava starch. This study will provide useful information of the micronized starch for its potential industrial application. [Copyright &y& Elsevier]

Abstract: High-pressure homogenization induced thinning of potato and cassava starch paste was investigated. The starch slurries at a concentration of 2.0wt.% were heated at 90°C for 1h and then rapidly cooled in tap water. The cooled starch pastes were homogenized at various pressures ranging from 0 to 100MPa using a lab-scale high-pressure homogenizer. The influence of homogenizing pressure on the temperature, apparent viscosity, electrical conductivity, and percent light transmittance of homogenized starch pastes were determined. Temperatures of homogenized starch pastes increased linearly with the increase of the applied pressure, and the rate was 0.177°C/MPa and 0.186°C/MPa for potato and cassava starch pastes, respectively. After high-pressure homogenization, the apparent viscosities of the starch pastes decreased, while the percent light transmittances of them increased. However, the electrical conductivities of starch pastes were not affected by homogenization. [Copyright &y& Elsevier]

Abstract: The effects of starch concentration on the rheological properties of dilute aqueous solutions of cassava starch were investigated. Cassava starch suspensions at different starch concentrations (0.2, 0.4, 0.6, 0.8, and 1.0 wt. %) were heated at 90°C for 1h and then rapidly cooled to 25°C. The apparent viscosities of starch solutions were measured as a function of starch concentration. The cassava starch solution with a concentration of 0.2% showed Newtonian behavior, and as the concentration was increased beyond 0.4%, the solutions showed shear-thinning behavior. The flow behavior (apparent viscosity against shear rate) of the solutions was well described using a power law model. The consistency indices increased and the flow behavior indices decreased with the increasing of starch concentration. After storing the solutions at 25°C for 24h, precipitation of starch took place instead of gelation. The volume of precipitation bed increased linearly with starch concentration. [Copyright &y& Elsevier]