Abstract: A process and an apparatus for converting liquid by-products, such as whey and permeates of whey, derived from cheese making processes into substantially free-flowing, non-caking powdery products. The process comprises the stages of vacuum evaporation of the whey to a solids content of 65-80%, crystallization of the whey concentrate and air drying the whey, wherein the main stream of initially cooled whey concentrate passing through stages of crystallization, is fed with a secondary and/or tertiary stream to be mixed with the main stream. The apparatus is provided with a secondary and/or a tertiary conduit for feeding a secondary and/or tertiary stream to the main stream in the main conduit connecting means for collection and pretreatment of whey, vacuum evaporation of the whey, crystallization of the whey concentrate and air drying the whey.