A method for treating starch in pulp， paper and board making processes

The invention relates to a method for treating starch in pulp， paper and board making processes， in which processes recycled fibre material is used as raw material wherein the recycled fibre material is pulped in a pulper and obtaining a pulp flow comprising an aqueous phase and at least recycled fibres and starch dispersed in the aqueous phase. The method comprising the following steps: - adding amylase enzyme inhibitor and/or at least one biocide to pulp flow or to an aqueous process flow comprising starch for preventing starch degradation， and - adding an amphoteric polymer obtained by copolymerisation of (meth)acrylamide with cationic and anionic monomers to pulp flow or to an aqueous process flow comprising starch for binding starch to the fibres.