Drying Methods of Coffee Extracts and Their Effects on Physicochemical Properties: A Review

Drying is one of the key steps in the coffee production process. It is necessary to dry the coffee extracts to prevent microbial growth and to prolong the storage time of coffee. To this date, mechanical drying methods have been developed and employed in industries to shorten the drying time. However, these drying methods could alter the physicochemical properties of coffee and the compounds present in coffee. Therefore, it is crucial to maintain these factors in the coffee production process as they affect the stability, reconstitution, and aroma of the coffee produced. These properties are crucial as they determine the final quality of coffee. This review will focus on the effect of spray-drying, freeze-drying, and spray-freeze–drying on the physicochemical properties of coffee such as morphology, particle size, moisture content, bulk density, and compound retention. Effects on organoleptic properties are also discussed. Possible advancements to these drying methods such as the encapsulation process, the use of a porous frozen sample, and total solid enhancement of the raw material have been highlighted.