Starches were isolated from cassava (Manihot esculenta) and potato (Solanum tuberosum) tubers. They were further modified by acetylation. The physicochemical, functional and thermal properties of native and modified starches, prepared using acetic anhydride at different times (10 and 20 min) were compared. Potato starch (Sipiera/20) showed higher acetyl percentage and degree of substitution values than cassava (2425/20) starch when acetylated for 20 min. Proximate analysis revealed that the acetylated starches retained more moisture than the native ones. Above 75 degrees C, acetylation improved the water binding capacity of the native cassava starch; the same trend was observed for potato starch from 60 to 90 degrees C after acetylation. The X-ray powder diffraction patterns derived from acetylated potato starches were similar to its native form, which was expected as B-type pattern; the same trend was observed for modified cassava starch. However the modified starches showed increased crystalline index. (C) 2011 Elsevier Ltd. All rights reserved.