The invention provides a method of continuously preparing caseinate from milk proteins in non-soluble powder form in an extruder machine having two co-rotating and interpenetrating screws into which water and an alkaline reagent are introduced, and the mixture formed by the milk proteins, the water, and the alkaline reagent is subjected to a plurality of steps of kneading under pressure and of shearing with the temperature rising to obtain at the outlet from the extruder machine a caseinate paste, the caseinate paste is cooled to bring its temperature to below 20.degree. C., a continuous thin sheet of caseinate paste is formed, and the sheet is cut up into a plurality of parallel strips, and these strips are cut up into small-sized pieces of caseinate. The invention also provides an installation for continuously preparing caseinate.