Applies to modified starch, both granular and soluble in cold water. The methods specified enable to measure total and free acetyl contents; bound acetyl content is calculated as the difference of the two values. Total content is determined by heating the sample with dilute hydrochloric acid and converting the acetate with adenosine-5-triphosphate (ATP) and coenzyme A (CoA) to acetyl-CoA. The methods are suitable for determining acetyl contents up to 2 % (m/m).