System for forming minced meat pieces from a mass of meat comprising: - a mould (12; 240) comprising at least one cavity (140; 245) for forming a minced meat piece; - a supply channel for supplying the mass of meat to the mould, characterized in that the system further comprises an interface element between the supply channel and the mould comprising: - a tubular section (24,25) having a first end connected to an outlet of the supply channel and an opposite second end connected to an inlet of the mould; - a grinding plate (28; 48) mounted at a level of the first end; which grinding plate comprises a series of orifices which extend through a thickness and are distributed over the surface of the grinding plate, the series of orifices having their axes parallel to the axis of the tubular section, - a grinding blade (27; 47) associated with the grinding plate and mounted upstream of the latter; and wherein: - the tubular section has - downstream of the grinding plate - a first part of truncated form receiving minced meat fibres at the outlet of the grinding plate arranged so as to enable a constriction of these minced meat fibres such that the minced meat fibres are substantially parallel to each other and constricted against each other so as to form a coherent set of parallel fibres, - the tubular section has - downstream of the first part and adjacent to this first part - a second part with a substantially constant cross section, in particular substantially cylindrical in shape, ending at a level of the second end, - wherein the tubular section is an open channel such that the coherent set of parallel fibres flows freely and without disruption along the second part of the tubular section and exits from the second end into the mould, - wherein the tubular section has a guide cone, which guide cone is assembled coaxially and extends in the first part of the tubular section, - wherein an elbow part is removably mounted on the first end of the tubular section; the interface forming element comprising disconnectable drive means (22, 30, 31, 26) for rotating the grinding blade, the drive means being assembled on the elbow part, a drive shaft (30, 26) extending in the elbow part coaxially to the tubular section, the grinding blade being assembled on the end of the drive shaft. - a mould (12; 240) comprising at least one cavity (140; 245) for forming a minced meat piece; - a supply channel for supplying the mass of meat to the mould, - a tubular section (24,25) having a first end connected to an outlet of the supply channel and an opposite second end connected to an inlet of the mould; - a grinding plate (28; 48) mounted at a level of the first end; which grinding plate comprises a series of orifices which extend through a thickness and are distributed over the surface of the grinding plate, the series of orifices having their axes parallel to the axis of the tubular section, - a grinding blade (27; 47) associated with the grinding plate and mounted upstream of the latter; - the tubular section has - downstream of the grinding plate - a first part of truncated form receiving minced meat fibres at the outlet of the grinding plate arranged so as to enable a constriction of these minced meat fibres such that the minced meat fibres are substantially parallel to each other and constricted against each other so as to form a coherent set of parallel fibres, - the tubular section has - downstream of the first part and adjacent to this first part - a second part with a substantially constant cross section, in particular substantially cylindrical in shape, ending at a level of the second end, - wherein the tubular section is an open channel such that the coherent set of parallel fibres flows freely and without disruption along the second part of the tubular section and exits from the second end into the mould, - wherein the tubular section has a guide cone, which guide cone is assembled coaxially and extends in the first part of the tubular section, - wherein an elbow part is removably mounted on the first end of the tubular section; the interface forming element comprising disconnectable drive means (22, 30, 31, 26) for rotating the grinding blade, the drive means being assembled on the elbow part, a drive shaft (30, 26) extending in the elbow part coaxially to the tubular section, the grinding blade being assembled on the end of the drive shaft.