The isolation of rice starch with food grade proteases combined with other treatments

The efficiency of starch isolations from milled rice with six food-grade protease preparations and combinations with ellulase, high-intensity ultrasound or defatting treatments were investigated. Alcalase and protease N 'Amano' (Protease N) were found to provide for a better separation of the rice starch from protein. Protease hydrolysis of the rice flour proteins combined with cellulase and defatting treatments lower residual protein content further to values which were similar to the conventional alkaline steeping method. Protein removal by hydrolysis with the two proteases was found to be most enhanced with a Cellulase pretreatment followed by initial pH adjustments of 10.5 for the alkaline protease Alcalase, and 8.5 for the neutral protease N. There were differences between the trough to final viscosities of the starches prepared with alcalase and protease N. There were no notable differences among different treatments of the isolated starches from the differential scanning calorimetry measurements. Most rice starch granules treated with protease showed no apparent surface damage as observed from scanning electron micrographs. Particle size distribution analysis revealed that the flour displayed bi-model size distribution. The higher sized fraction (10 to 100 mu m) decreased rapidly when protease treatments were applied. The isolation of rice starch with proteases combined with other treatments could produce rice starch with native structure, limit the waste products from the separation process and provide a prospective for the design of a commercial process.