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. Said diafiltration stage permits both the degree of washing of the product and the quality and amount of the product retentate and the permeate that is produced to be set and regulated within a wide range, even for fixed operating conditions, such as those required in continuous multi-stage large-scale installations.
