Press for separating the solid and liquid parts of matter such as the grape harvest, comprising: - a cage presenting a cylindrical lateral wall and two flanges closing said cage respectively at one end and at the other end of said lateral wall; - means (4, 13-16) of mounting said cage to rotate about its axis in a position where the latter is positioned horizontally, comprising a chassis (4, 14, 16); - means for selectively controlling the rotation of said cage about its axis; - a deformable flexible membrane positioned in said cage, fixed in a seal-tight manner to the lateral wall of the cage along two opposite longitudinal edges and fixed in a seal-tight manner to the flanges along two respective transversal edges each situated between an end of one longitudinal edge and an end of the other longitudinal edge so that said membrane separates the internal volume of said cage into a pressing chamber delimited by said membrane, by a first half of said lateral wall situated between said two opposite longitudinal edges and by a first half of each of said flanges situated, relative to the respective transversal edges, alongside the first half of the lateral wall, and into a control chamber delimited by said membrane, by the second half of said lateral wall and by the second half of said flanges, said flexible membrane, at rest, having almost the form of half of the cage; - means (13, 17) of admitting a pressure agent into said control chamber and means (13, 18) of sucking said pressure agent out of said control chamber; - at least one door blocking or revealing an opening provided in said first half of the lateral wall of the cage; - drainage means equipping said first half of the lateral wall of the cage; and - means of recovering said liquid part of the matter leaving the pressing chamber via said drainage means; characterized in that said recovery means comprise: - on the cage, at least one external racking device, and a connection unit through which opens out the outlet orifice of the racking device; and - on said chassis (4, 14, 16, 42, 43), a liquid sampling device comprising a telescopic tubular unit accepting a retracted position in which said telescopic unit presents no obstacle to the rotation of the cage and an extended position in which said telescopic unit is adapted, when the cage is in a predetermined pressing angular position, to come against said connection unit in a seal-tight bearing manner around the outlet orifice of the racking device; said connection unit being a plate projecting radially from the lateral wall whereas said telescopic unit comprises an annular sealing gasket by which said telescopic unit is adapted to come into contact against said plate about said outlet orifice. - a cage presenting a cylindrical lateral wall and two flanges closing said cage respectively at one end and at the other end of said lateral wall; - means (4, 13-16) of mounting said cage to rotate about its axis in a position where the latter is positioned horizontally, comprising a chassis (4, 14, 16); - means for selectively controlling the rotation of said cage about its axis; - a deformable flexible membrane positioned in said cage, fixed in a seal-tight manner to the lateral wall of the cage along two opposite longitudinal edges and fixed in a seal-tight manner to the flanges along two respective transversal edges each situated between an end of one longitudinal edge and an end of the other longitudinal edge so that said membrane separates the internal volume of said cage into a pressing chamber delimited by said membrane, by a first half of said lateral wall situated between said two opposite longitudinal edges and by a first half of each of said flanges situated, relative to the respective transversal edges, alongside the first half of the lateral wall, and into a control chamber delimited by said membrane, by the second half of said lateral wall and by the second half of said flanges, said flexible membrane, at rest, having almost the form of half of the cage; - means (13, 17) of admitting a pressure agent into said control chamber and means (13, 18) of sucking said pressure agent out of said control chamber; - at least one door blocking or revealing an opening provided in said first half of the lateral wall of the cage; - drainage means equipping said first half of the lateral wall of the cage; and - means of recovering said liquid part of the matter leaving the pressing chamber via said drainage means; - on the cage, at least one external racking device, and a connection unit through which opens out the outlet orifice of the racking device; and - on said chassis (4, 14, 16, 42, 43), a liquid sampling device comprising a telescopic tubular unit accepting a retracted position in which said telescopic unit presents no obstacle to the rotation of the cage and an extended position in which said telescopic unit is adapted, when the cage is in a predetermined pressing angular position, to come against said connection unit in a seal-tight bearing manner around the outlet orifice of the racking device;