Process and product characteristics of refractance window dried Curcuma longa

This work addresses the optimality of hot water bath based refractance window drying (RWD) characteristics of 1 mm Curcuma longa (turmeric) slices. Mylar film thickness (125 to 350 µm) and water bath temperature (65 to 95 °C) have been considered as independent variables to evaluate drying kinetics and nutritional characteristics of the process product combination. Equilibrium drying time, moisture diffusivity, fitness of thin layer models, moisture content, total phenolic content, total flavonoids content, curcumin content, and antioxidant activity have been considered to evaluate the optimality of the RWD process parameters. It has been analyzed that while both parameters critically influence equilibrium drying time, only temperature had profound influence on nutritional characteristics. PRACTICAL APPLICATION: There is a need for a fast-drying method without significant loss in bioactive compounds. Refractance window drying (RWD) method is such a process. The study of RWD of turmeric slices will help in understanding the relations between different drying temperatures and mylar film thickness and its relation to nutritional characteristics of the product.