Abstract: The invention relates to a method of crystallizing lactose from a lactose-containing liquid comprising the steps of providing a lactose-containing liquid comprising less than 80% by weight total solids, providing an evaporator system that comprises a heat exchanger and an evaporation vessel, the heat exchanger comprising a tube or tubes that define a flowpath having an inlet and an outlet, heating the lactose-containing liquid in the heat exchanger to about 50 to about 90° C. such that the lactose-containing liquid passes along the flowpath by forced circulation or thermo-siphoning, concentrating the lactose-containing liquid in the evaporation vessel, to generate crystallized lactose in the lactose-containing liquid in the evaporator system.