Vertical batch freezer (1) for preparing a pasty food product, comprising at least one tub (2) open on top and having a side wall (2a) and a lower base (2b), at least one refrigeration cylinder (3) provided with a cavity (3 a) inside which said tub (2) is at least partially housed, said refrigeration cylinder (3) further comprising cooling means (4) to cool said pasty food product contained in said tub, said cooling means comprising at least one tubular duct (5) for passing a coolant, which extends along a curvilinear longitudinal axis (Z) arranged around and/or underneath at least part of said cavity, said duct (5) comprising at least one outer perimetrical surface (7) having a heat exchange zone (7a) facing said side wall (2a) and/or said lower base of said tub to directly exchange heat with the food product contained in said tub, characterized in that said heat exchange zone (7a) has, for at least one portion (5a) of said duct (5), along said curvilinear longitudinal axis (Z), cross section (9) having a substantially straight length (10a) facing said side wall (2a) and/or said lower base (2a) of said tub (2), said heat exchange zone (7a) being defined by the translation of said substantially straight length along said curvilinear longitudinal axis (Z) of said duct.
