A shredder assembly for a food waste disposer that includes an impact mechanism for freeing jams. The impact mechanism uses the stored energy in the rotating portion of the disposer's rotating elements to be transmitted from the rotor shaft via an impact member to a part of the rotating shredder assembly. The shredder assembly includes a rotatable shaft and an impact member fixedly attached to the shaft to rotate therewith. A shredder disk is attached to the shaft via a clutch allowing the shredder disk to slip relative to the shaft when the shredder disk jams, wherein the impact member strikes the shredder disk to transfer rotational energy to the jam.