Abstract: The invention relates to a diafiltration stage for concentrated fruit juices, comprising a cross-flow filtration element (1). The product inlet (2) and the product outlet (3) of the filtration element (1) are united via a circulation pump (5) to form a product circuit, to which product is continuously supplied via a product supply line (6) and from which product can be continuously removed via a product discharge line (8). The permeate outlet (4) of the filtration element (1) is connected to the product circuit via a return line (1) comprising a permeate pump (13), enabling a desired amount of permeate to be returned to the product circuit. In addition, the stage comprises a wash-fluid supply line (10) that is equipped with a wash-fluid pump (12), which is used to supply a desired amount of water to the product circuit as wash fluid. The supplied amounts of permeate and water can be set independently of one another.