The invention relates to a device and a method for the continuous decomposition of starch by means of a reaction container (2) for producing enzymatically decomposed starch paste, a first transport section (4, 7, 21, 22) for a volumetric flow of the starch paste having at least one pump (5) and an inactivation device (6) for heating the starch paste to the inactivation temperature of the enzymes. The invention is characterised in that the first transport section (4, 7, 21, 22) provides a circuit of the starch paste between the reaction container (2), pump (5) and inactivation device (6) and a second transport section (23) is provided, by means of which at least one part-stream of the starch paste is transferred from the first transport section (4, 7, 21, 22) downstream of the inactivation device (6) into a storage container (11) or for further processing.