Which of the following methods does NOT remove water by evaporation?

The correct answer is the freeze dryer. Freeze drying, or lyophilization, is a process that involves freezing the material and then reducing the surrounding pressure to allow the frozen water in the material to sublimate directly from ice to vapor without passing through a liquid phase. This method removes water effectively but does not rely on evaporation, which typically involves turning liquid water into vapor through heating.

Air drying, spray drying, and slow drying all primarily utilize heat to facilitate the evaporation of water from the material. In air drying, moisture is removed by the slow circulation of air at ambient temperature. Spray drying involves atomizing a liquid into a hot gas stream, promoting rapid evaporation. Slow drying, as the name suggests, involves gradually removing moisture at low temperatures, typically through the application of heat. Each of these methods depends on evaporation as a means of moisture removal, unlike freeze drying.