The present invention relates to a method of preparing a starch-based composition, characterized in that it comprises: (a) mixing a starch substrate with sodium perborate; (b) adding water to the mix of step (a) to form a slurry; and (c) pasting the slurry of step (b), provided that the method does not include, between steps (b) and (c), the step of adding an effective amount of hydrolytic enzyme to the slurry. The invention further relates to starch-based compositions prepared in accordance with said method, paper sizing and/or coating compositions comprising said starch-based compositions and paper products treated with said sizing and/or coating compositions.