The antisolvent vapor precipitation approach was introduced to recover soluble protein in the waste whey stream from cheese manufacture. This technique involved exposing a droplet of the whey protein containing liquid to an ethanol vapor–laden convective medium. The soluble protein and lactose will tend to precipitate due to the absorption of ethanol into the droplet. Experiments were undertaken with lactose, whey protein isolate (WPI), WPI + lactose, and sweet whey droplets. It was found that lower droplet pH, controlled by the addition of lactic acid, precipitated long, flat lactose crystals. At pH condition in proximity to the isoelectric point, the antisolvent vapor precipitation technique produced fine and semi-uniform whey protein particles dispersible in water. Precipitation of WPI + lactose droplets revealed that a blend of crystalline lactose with fine particles can be produced simultaneously. Further experiments with sweet whey droplets showed that the presence of calcium phosphate retards the precipitation of the fine particles, resulting in a highly agglomerated morphology.

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