Effect of blending and pregelatinizing order on properties of pregelatinized starch from rice and cassava

Abstract

The aim of this work was to investigate the effects of processing order by mixing and pregelatinizing on properties of pregelatinized starch blends of cassava (C) and rice (R) starches, either mixed in various ratios (0, 10, 30, 50, 70, 90 and 100%C) before pregelatinizing (MP) or with that order exchanged (PM, for pregelatinizing the components before mixing). Starch solids of 45% in water were pregelatinized using double drum drying at 120oC. The water absorption index (WAI) and water solubility index (WSI) were measured, and pasting properties were characterized using Rapid Visco Analyzer (RVA). The results showed that MP (30 - 70%C blends) had WSI half of that of PM, while with 10%C the former gave the higher WSI. In RVA viscosities, especially the hot peak viscosity, MP cases had significantly higher values (p<0.05) than PM for all mixing ratios, indicating interactions in MP and less degradation of starch molecules. The choice of processing order gives some additional control over pregelatinized starch blend behavior in water, while a larger range of control is available by selection of the blend proportions.