A method of producing a beta-casein-containing composition containing at least 50% (w/w) beta-casein relative to the total amount of casein and at least 30% (w/w) beta-casein relative to the total amount of proteins, the method comprising the steps of: a) pre-heating a milk by adjusting it to a pre-heating temperature (T pre) of at least 20 degrees C, said milk is kept within the pre-heating temperature range for a duration t pre of at most 24 hours thereby providing a warm milk, b) subjecting the warm milk to microfiltration, wherein the temperature of the feed during MF of the warm milk is maintained at a temperature (TwMF) of at least 20 degrees C and using a filter that retains at least a substantial fraction of the casein micelles, but allows for the passage of milk serum protein thereby providing a first MF permeate and a first MF retentate, c) subjecting the first MF retentate to MF-diafiltration, using a first diluent having a pH in the range of 6-8, and wherein the temperature of the feed and retentate stream is kept within the warm MF temperature range during at least part of the MF-diafiltration, d) adjusting the temperature of a first composition derived from the first MF retentate, said first composition comprises a total amount of casein of at least 90% (w/w) relative to the total amount of protein of the first composition, to a cold temperature (T cold) in the range of 0-15 degrees C and keeping the temperature of the first composition within that range for a duration (t cold) of at least 0.5 hour, thereby obtaining a cooled first composition, e) subjecting the cooled first composition to MF, thereby obtaining a second retentate and a second permeate, which second permeate is enriched with respect to beta-casein, and f) optionally, subjecting the second MF retentate to MF-diafiltration, g) optionally, subjecting a second composition derived from the second permeate to one or more further processing steps, e.g. further purification and/or concentration steps, thereby providing the beta-casein-containing composition. a) pre-heating a milk by adjusting it to a pre-heating temperature (T pre) of at least 20 degrees C, said milk is kept within the pre-heating temperature range for a duration t pre of at most 24 hours thereby providing a warm milk, b) subjecting the warm milk to microfiltration, wherein the temperature of the feed during MF of the warm milk is maintained at a temperature (TwMF) of at least 20 degrees C and using a filter that retains at least a substantial fraction of the casein micelles, but allows for the passage of milk serum protein thereby providing a first MF permeate and a first MF retentate, c) subjecting the first MF retentate to MF-diafiltration, using a first diluent having a pH in the range of 6-8, and wherein the temperature of the feed and retentate stream is kept within the warm MF temperature range during at least part of the MF-diafiltration, d) adjusting the temperature of a first composition derived from the first MF retentate, said first composition comprises a total amount of casein of at least 90% (w/w) relative to the total amount of protein of the first composition, to a cold temperature (T cold) in the range of 0-15 degrees C and keeping the temperature of the first composition within that range for a duration (t cold) of at least 0.5 hour, thereby obtaining a cooled first composition, e) subjecting the cooled first composition to MF, thereby obtaining a second retentate and a second permeate, which second permeate is enriched with respect to beta-casein, and f) optionally, subjecting the second MF retentate to MF-diafiltration, g) optionally, subjecting a second composition derived from the second permeate to one or more further processing steps, e.g. further purification and/or concentration steps,