Abstract:In order to obtain a suitable moisture content of starch for mechanical activation and to improve the mechanical activation effect for reducing the duration of mechanical activation, the influence of the moisture content on the physicochemical properties of mechanically activated rice starch isolated from three rice cultivars was investigated. The results indicated that when the duration of mechanical activation was prolonged, the gelatinization degree, cold-water solubility, transparency, and reducing power of rice starch increased, while the blue value (BV) decreased. Indica rice starch was easily decomposed by mechanical force when the moisture content was 6.02%, while the moisture content of Japonica rice starch and glutinous rice starch was about 8.50%. In terms of the gelatinization degree and cold-water solubility, Indica rice starch reached the maximum value at a moisture content of 6.02%, while Japonica rice starch and glutinous rice starch reached the maximum at about 8.50%. For transparency, all three rice starches reached the maximum value at a moisture content of about 8.50%. Regarding the reducing power and the BV, Indica rice starch exhibited the most rapid change at a moisture content of 3.50%, while that of Japonica rice starch and glutinous rice starch was determined at about 6.00%. It was concluded that the moisture content had some influence on the mechanical activation of rice starch, and moisture contents of 6.00%~8.50% were determined as the optimum for mechanical activation.
