Comprehensive Review on Drying of Turmeric Rhizomes

Turmeric (Curcuma longa L.) is widely used for its pungent and aromatic flavours and medicinal properties in foods. In the last three years, several studies have witnessed turmeric gaining more economic importance due to its medicinal value against COVID-19. In addition, it has been used for many other medical treatments due to its antimicrobial properties, indicating that it has significant potential in clinical medicine. In view of its importance in the health sector, preserving turmeric is very important to make it available for a longer period. Among the food preservation methods, drying is one of the simplest and oldest methods for increasing the shelf life of agricultural produce. Curcumin is an active ingredient of turmeric, and it is more sensitive to heat and light. Some researchers observed that the direct sunlight, temperature and duration of drying have significant effects on the concentration of curcumin in the turmeric. Open sun and shade drying methods consume a lot of energy and time. In addition, open sun drying samples do not retain maximum curcumin content. Meanwhile, solar dryers provide heat indirectly to the turmeric rhizomes by covering polyethene sheets or glass. Thus, the turmeric rhizomes are able to dry without losing curcumin content in less time than conventional drying methods. Further, microwave drying, infrared drying, and freeze drying can also be used, but these are not economically feasible for farmers. This paper briefly describes the drying status of turmeric rhizomes in the last two decades.