Drying of Selected Major Spices: Characteristics and Influencing Parameters, Drying Technologies, Quality Retention and Energy Saving, and Mathematical Models

Demand for value-added spices all year round has warranted suitable post-harvest processing, since most are non-perennial by nature and perishable owing to enzymatic or maillard reactions and pathogenic microbial contamination. Drying involves the minimization of biologically active water up to the safe water activity level and increases the shelf life. An optimized drying technique is needed to be chosen critically because one particular drying condition suitable for a group of spices may be detrimental for others. Therefore, the current review emphasizes the permissible ranges of influencing operating parameters, comparative effects of several drying technologies on drying characteristics, and quality attributes of spices. The paper also provided an up-to-date technological advancement in novel hybrid and staged drying to alleviate the shortcomings of a solo drying technique. As drying is an energy-intensive process, pre-drying treatments and intermittent phenomena have also been explored for energy saving with better quality retention. The paper also highlights the significance of thin layer modeling for predicting the moisture transport phenomena during drying.