Process for the production of a three-dimensional item by extrusion and deposition of a string of dough, comprising the following steps: a) providing an extruder comprising a cylindrical tubular body having a first end closed by a bottom having at least one nozzle and a second end, and a piston comprising a rod and a piston head that can be removably coupled to one another; b) feeding a viscoelastic food dough into said cylindrical tubular body; c) providing said piston inside the side wall of said cylindrical tubular body, said piston head being in contact with said side wall of said cylindrical tubular body and freely slidable inside said cylindrical tubular body, and said viscoelastic food dough being entirely contained between said piston head and said bottom; d) extruding said viscoelastic food dough by progressively advancing said rod and said piston head, said piston head being coupled with said rod and pushed by it, inside said cylindrical tubular body towards said bottom of the cylindrical tubular body along a sliding path, resulting in the supply at a preset speed of a continuous string of dough from said at least one nozzle; e) interrupting the extrusion of said viscoelastic food dough by stopping the progress of said rod at a specific position along said sliding path and by immediate movement of said rod towards said second end, in order to decouple said rod from said piston head and let said piston head be pushed by said viscoelastic dough towards said second end of the cylindrical tubular body; wherein the progress of said rod inside said cylindrical tubular body towards said bottom and the movement of said rod towards said second end are controlled by means of a control system of the extruder; and during said step e) of interrupting extrusion of said viscoelastic food dough, said specific position of said rod along said sliding path corresponds to a preset position previously saved by said control system of the extruder or said specific position of said rod along said sliding path is recorded by said control system of the extruder at the time when said rod is separated from said piston head. a) providing an extruder comprising a cylindrical tubular body having a first end closed by a bottom having at least one nozzle and a second end, and a piston comprising a rod and a piston head that can be removably coupled to one another; b) feeding a viscoelastic food dough into said cylindrical tubular body; c) providing said piston inside the side wall of said cylindrical tubular body, said piston head being in contact with said side wall of said cylindrical tubular body and freely slidable inside said cylindrical tubular body, and said viscoelastic food dough being entirely contained between said piston head and said bottom; d) extruding said viscoelastic food dough by progressively advancing said rod and said piston head, said piston head being coupled with said rod and pushed by it, inside said cylindrical tubular body towards said bottom of the cylindrical tubular body along a sliding path, resulting in the supply at a preset speed of a continuous string of dough from said at least one nozzle; e) interrupting the extrusion of said viscoelastic food dough by stopping the progress of said rod at a specific position along said sliding path and by immediate movement of said rod towards said second end, in order to decouple said rod from said piston head and let said piston head be pushed by said viscoelastic dough towards said second end of the cylindrical tubular body; wherein the progress of said rod inside said cylindrical tubular body towards said bottom and the movement of said rod towards said second end are controlled by means of a control system of the extruder; and during said step e) of interrupting extrusion of said viscoelastic food dough, said specific position of said rod along said sliding path corresponds to a preset position previously saved by said control system of the extruder or said specific position of said rod along said sliding path is recorded by said control system of the extruder at the time when said rod is separated from said piston head.