Spray drying is a method of drying solutions, including the production of instant coffee. In this process, the substance is atomized into fine droplets and then dried by hot air. In the case of coffee, it is pumped into a drying tower and quickly dried to a fine powder. The resulting powder can be re-dissolved with water to make an instant coffee beverage. Spray drying is also used to convert other substances such as milk into powder form.
The process of spray drying begins by spraying the substance into the drying tower, where hot air circulates. The atomized droplets dry quickly and form a fine powder at the bottom of the tower. A cyclone separator is often used to separate the powder from the air flow. The spray-dried coffee powder can also undergo agglomeration, which uses steam to agglomerate the fine particles into larger coffee granules, typically found in instant coffee.
Although spray drying is one method of producing soluble coffee, there are also alternative processes such as freeze drying. In this process, the coffee extract is foamed, frozen, and then the frozen water is sublimated in a vacuum dryer. The remaining solid component is the instant coffee. Both spray drying and freeze drying result in soluble coffee without additional additives.