A single effect evaporator is used to concentrate a fruit juice from 10 to 45% soluble solids. The evaporator is fed with 2500 kg/h at a temperature of 52 C. Steam at 121.1 C is used as heating medium, which enters a heat exchanger placed inside the evaporator and is condensed. The boiling point of the juice is 57 C and at that temperature the concentrate leaves and the vapor is released from the juice.