Abstract: During milking of dairy animals, the produced milk is membrane filtered and transported to a container or other end unit (1). From this end unit, the milk is led by way of a balance tank (6) to a circulation path, of which the membrane filter (10) is a part. The permeate obtained during membrane filtration is returned to the end unit and used to press forward milk from the end unit and from the other equipment in the filtration unit between the end unit (1) and the membrane filter (10).

Abstract: In order to produce a milk concentrate by membrane filtration of the milk produced at a milking plant the milk is during the milking continuously led to the concentrate space (2) of a member filter unit (1) possibly after heating to a temperature of 50.degree.-70.degree. C. The degree of concentration of the outgoing concentrate from the concentrate space is determined in that two positive pumps (13, 16) are arranged to work at a constant internal relation in capacity each arranged to control a flow chosen among arriving milk flow to the concentrate space (2), outgoing concentrate flow from the concentrate space (2) and outgoing permeate flow from the permeate space (3) of the membrane filter unit (1).