Production of amorphous starch powders by solution spray drying

The spray drying of starch/maltodextrin formulations was evaluated as a potential technology for the manufacturing of amorphous thermoplastic starches. Mixtures of starches with high to low amylose (Am)-amylopectin (Ap) ratios were spray-dried from water-based solutions and granular dispersions. The effects of the feed composition on the morphology and physical properties of the end product were investigated with the spray-drying conditions kept constant. Powders obtained from the starch solutions were totally amorphous, and the particle size characteristics were not affected by the applied variations in composition. The particles obtained from the solution-dried formulations were small, highly irregular, and shriveled, and the bulk densities were low. Independent of the Am/Ap ratio, the particles could easily be redissolved and showed low viscosities. The spray-dried powders obtained from the starch-water dispersions very much retained the granular structure present in the native components. All showed viscosities, crystallinity patterns, gelatinization, and powder flow characteristics in line with expectations for Am/Ap-based granular mixtures.