Drying turmeric ( Curcuma longa L.) using far‐Infrared radiation: Drying characteristics and process optimization

What is it about?

This study aimed to investigate the drying characteristics of turmeric and optimize the process parameters for far-infrared (FIR) radiation drying. Sliced wet turmeric samples with an initial moisture content of approximately 80 ± 0.12% (wb) were subjected to FIR radiation at wavelengths of 6.65, 5.97, 4.97, and 4.80 μm for varying durations of 70, 30, 25, and 20 minutes, respectively. The moisture content and color parameters (L*, a*, and b* values) of the turmeric were measured throughout the experiment. Optimization experiments were conducted using response surface methodology and a central composite design, with two independent variables: exposure time and FIR wavelength. The dependent variables considered were moisture content, curcumin content, energy consumption, and color-changing index. The results showed that as the FIR radiation wavelength decreased, the final moisture content and curcumin content of turmeric decreased as well. The drying process using FIR radiation was found to be a falling rate process. The optimal conditions were determined to be a FIR wavelength of 5.51 μm and an exposure time of 21 minutes using the desirability function method. Under these optimal conditions, the predicted values for the response variables were as follows: curcumin content of 3.26% (dry weight), color-changing index of 13.29, energy consumption of 2.51 kWh/g water, and final moisture content of 10.25% (wb). The desirability value of 0.8157 under the optimal conditions confirmed the validation of the models.

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Photo by Dyah Miller on Unsplash

Photo by Dyah Miller on Unsplash

Why is it important?

Far-infrared radiation can be utilized for industrial-scale drying of turmeric. The drying rates and color-changing index of turmeric were found to increase with shorter far-infrared wavelengths and longer exposure times. Additionally, curcumin content decreased as the far-infrared wavelength and exposure time increased. Overall, the results concluded that FIR radiation can be effectively applied for drying turmeric.